Is vapor locking possible

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I am getting beat up here, i have a 87 tbi 454 Silverado 20, not quite 70k on it. I had fuel problems with it a few months back and replace the pumps, screens, switches and redid the grounds. the truck has run fine except for a couple of time this summer when i parked it and it did not restart and i had to flip the tank switch and it would start fine. i thought it might just be a bad hot start, today my daughter was driving it down to road and stopped to turn into a drive and the truck just died, she tried restarting to no avail, she flip the tank switch a couple of times. Some people helped her get it to a safe location, and i called a tow truck for it. when the tow truck got there they were able to start it right up and it ran fine. I live in the Phoenix area and we have been having 110 - 117 days, is it possible that it vapor locked? any ideas?