Year of aircraft, engine model, carb or injected?
Not sure if it was vapor lock, but I've had a 172SP (Lyc IO-360) that after landing wouldn't idle on a toasty high DA day at a 6000MSL airport no matter how I leaned the mixture. Seemed to run fine at higher power settings, though. Flew back to a lower altitude and it never did that again.
Vapor lock doesn't only affect carb'd engines, it can affect FI systems as well. Often times, the reason a fuel injected engine has trouble starting, has a lot to do with vapor in the system, which prevents fuel from getting into the cylinders. The fuel pump has difficulty purging vapor in the pump and fuel lines. When the engine is shutdown after a flight, it's hot, which allows heat to draw into the fuel lines including the fuel pump and vapor can form.I think vapor lock is fairly unusual in an injected engine, but there is a first time for everything (and you are never too old to learn).