I've vapor locked twice in my '95 Nissan Sentra, both times at high altitude (> 8000MSL), after having driven at freeway speeds to get there. The lock was at startup; engnie would crank normally but not fire, then run rough ~15 sec after catching.
One time I simply cranked it until it caught (letting starter cool as I went); the other time, I had the advantage of being atop a hill, so I roll-started it when it wouldn't start normally.
I don't think Diesel has anything to do with octane here; I think the higher-carbon Diesel reduces the overall volatility of the fuel. Also, I was under the impression ethanol had a lower vapor pressure than gasoilne.
I know the (fuel-injected) A36 Bonanza vapor-locked frequently; there was even a "vapor-locked startup" checklist, so I don't know why it couldn't happen in a FI car.