Hydrolock happens, though I dare say it happens far less often than you read on this interweb thingy.
Pull the plugs, crank a few turns (just in case), plugs back in, start, listen. If it had hydrolocked in the past, and bent a connecting rod, you'll know it.
Can also set up a dial indicator (plunger type) to measure plug seating surface to top of piston on all cylinders, but several variables. Mostly carbon build up on piston crown. A compression or differential leak down test should also work. As will a bore scope to detect any major scoring of the cylinder walls.
New petcock advised, OEM is fine (though many will disagree). Internal rubber bits may be near end of life, especially considering the low miles.
Rick