Here's how to travel when you've lost your ID, phone or wallet 

Sally French is admittedly forgetful. On a flight to Washington, D.C., the travel expert with NerdWallet left her wallet in an airplane seat pocket. In Croatia, she drove off in a rental car without her passport. When she returned to the counter to retrieve it, the critical document had vanished.

In both predicaments, French knew exactly what not to do: freak out. Instead, she calmly figured out how to recover what she had lost or how to manage without it.

"It doesn't have to be catastrophic," she said. "Always be flexible and always have a backup plan."

When we travel, some items are expendable or easily replaceable; others are more vital and difficult to recover. Without these essentials, we may find ourselves stuck — in a hotel parking lot (lost rental car key), at airport security (missing driver's license) or in a foreign country (mislaid passport).

What to do if you lose a rental car key

Gregory Scott, a spokesman for the American Car Rental Association, said the industry does not have a standard lost key policy, but generally you will need to contact the rental car counter or roadside assistance. Depending on the circumstances, the company will hand over a spare key or provide you with a new vehicle if they don't have an extra key.

If you opted out of insurance, you will have to pay for roadside help and the duplicate key. Hertz charges a flat fee of $250 for a key replacement.

"Whether they can bring you another key or order another, a fee is involved unless you purchased a protection plan," Scott said.

What to do if you lose your driver's license

Driver's licenses are really only important if you are flying domestically, renting a car or barhopping.

For air travel, the Transportation Security Administration accepts alternate forms of identification, such as passports; trusted traveler cards like Global Entry and NEXUS; a Defense Department ID, among others.

If you have none of the above, all is not hopeless.

According to the agency, the officer may ask you to complete an identity verification process, which could involve providing your name, address and other personal information. Once the officer confirms your identity, you can proceed to the screening checkpoint, but you will be subjected to additional screening, such as a pat-down. Because of the extra steps, TSA recommends arriving at least two hours before your flight.

If your travel mate has a valid driver's license, try to switch the reservation to their name. However, you will not be permitted to drive the vehicle.

What to do if you lose your passport

As soon as you notice that your passport is MIA, notify the nearest U.S. embassy or consulate. Report your lost passport and share your travel itinerary with officials in the consular division, especially if you have imminent plans to leave the country.

To acquire a replacement or "limited-validity, emergency" passport, you must physically appear at the embassy or consulate during the workweek. The staff will need to see identification, such as a driver's license; proof of U.S. citizenship, such as a copy of a birth certificate or a photo of your passport; and your trip itinerary — though missing any of these documents doesn't mean you are destined for an expat lifestyle. Also required: a passport photo and a completed DS-11 application and DS-64 statement explaining your situation. The forms are on the agency's website, as is the contact information for the embassy or consulate. If you received an emergency passport, you will need to reapply for a regular passport once you are home.

What to do if you lose your wallet

Only bring credit cards and IDs that you frequently use. Make sure your phone number or email address is visible in your wallet, so the finder knows how to return your valuables.

Once you notice you're missing credit cards, sign into the company's online account or the app and activate the lock feature to prevent anyone from taking your cards on a shopping spree. Take similar precautions with your bank card. If you find your wallet, you can easily reactivate your cards.

If you don't have an online account or the app, call the companies to report your lost cards. Most firms have toll-free numbers for domestic calls and accept collect calls internationally. If you think your card is forever gone, order a replacement with a new card number.

When French lost her wallet, she didn't have to curb her spending. She used Apple Pay for purchases that required a credit card and took out money by scanning her phone at the ATM.

What to do if you lose your phone

In the event of a lost smartphone, Nicholas De Leon, a senior reporter with the Consumer Reports' electronics team, recommends travelers take a proactive approach instead of jumping right into reaction mode.

"We break up our advice into before and after," he said.

In the before period, he suggests protecting your phone with a strong password, your first line of defense. Also turn on your phone's biometric authentication system, such as facial recognition or fingerprint reader, and activate the "Find My" tool; Apple and Android have versions of this. Most important, back up all of your contacts, photos, text messages and files by uploading your valuable information to the cloud.

As an extra layer of protection, email to yourself essential documents, such your travel reservations, emergency contacts and a photo of your passport.

Once you realize that your device is missing, try to track its whereabouts with the "Find My" feature.

If that tool fails, contact your service provider to report the loss and ask them to disable your device. For an extra layer of protection, change all of your passwords, especially on apps that are linked to your credit card or financial services, and turn off Apple Pay. You can also wipe your gadget clean.