Don't go crazy trying to figure this out, an engine needs 3 things to run,
fuel, spark and compression, since this engine ran great when you parked
it, it has to be fuel or spark, so to test fuel, shoot some starting fluid into
the intake, take off the air cleaner and give it a 1 second burst, turn the key,
if it starts and stalls, you have a fuel system problem, if it doesn't start you
have an ignition problem.
Go try this and report back what happened
Wild