Vapor lock was much more common in cars of the 40’s and 50’s and seems so rare today that I wonder if you really experienced vapor lock. Old cars with mechanical fuel pumps only develope about 4-5 lbs of pressure. The high heat in the engine compartment combined with high ambient temperatures could get so high that the liquid fuel would vaporize in the fuel line(s) leading to the carburator. The carburator is set to vaporize liquid fuel and couldn’t handle fuel already vaporized and the car would stop. You’d open the hood and wait for the motor to cool or for a quicker fix carry water in the car to dump on the fuel lines to cool them and then fire up the car and be off.
Fuel at higher pressures does not vaporize in the fuel lines and modern cars with fuel injection all use high pressure systems. To get vapor lock in your car you’d need a problem such as a weak fuel pump that is not producing the high pressures it is supposed to generate.
Instead of vapor lock what is more common in today’s cars is the electrical components overheat and heat kills electronic things pretty fast.
I’m not saying you didn’t experience vapor lock, but if you did it is very unusual in a car such as yours. I don’t know about the cupful of diesel, and I don’t think the differences in vaporizing of regular or premium fuel is much different. Perhaps a pressure test of your fuel pump would be advisable?