Learned a lesson on a recent road trip to Washington, D.C.

Keep a copy of your auto insurance card — with the VIN (Vehicle Identification Number) — in your wallet. If your car has never had its locks changed, an auto dealer can issue you a new key.

The insurance card was essential when I locked my keys in the trunk — Don’t ask how — because Toyota dealers have a rule about making new keys: You must show either a vehicle registration card or an insurance card with the VIN number and a drivers license issued to the same name.

Otherwise, says Toyota, you could be a thief who simply copied the VIN number. I keep my car registration in the car, which was locked, so the insurance card in my wallet was my only hope unless I wanted to break into my own car or hire a locksmith.

I borrowed a car, drove to Bethesda, Md., and less than $10 later, I had a new key from Toyota. This would have been much more expensive if Toyota had been asked to replace one of those non-key keys with the computer chip inside — reason enough to be happy with the old-fashioned key.

I put the insurance card in my wallet because occasionally I’m asked to prove insurance when I rent a car. Now I know another reason to carry that card.