I doubt it was vapor lock, unless you have a defective fuel injector. The fuel is held at high pressure until injected into the engine, altitude should have no effect (otherwise you’d see lots of cars at the side of the road in high altitude areas). I also recommend against the diesel solution. Premium sure won’t hurt, but I don’t know why it would help. Both would increase the octane (make the fuel harder to burn). If was me, and assuming no codes were created in the computer (did no lights go on?), I might run the max dose of Techron fuel treatment through it (get it at Walmart, read the label) and run premium, just in case. But that’s all just based on hoping it cures a problem I can’t explain…