I once had a problem with the ignition lock I couldn't turn the key, my mechanic told me that that could happen on a very hot day with that model. "use a lubricant or wait till it's colder" - "Would WD-40 do?" -"Guess so" made it worse. with the help of the AAA (well, the equivalent in my country) and an oil spray I could turn the key, since then I've always an oil spray with me

Had the same problem with my moto (key not turning the lock). Fortunately, there was a car nearby and owner had a spare jug of oil. I put some oil on the key, put it in the ignition lock, waited for 5 minutes, and it started to turn again.

Although I must admin WD-40 helped me in the past opening an old door lock.