I'm a motocross racer, plus i Do all my own work, and used to race sprint cars as well. I've seen Hydro locked motors. Ususally happens when ur motor is literally filled with liquid, namely antifreeze. I've never seen it in anything with more than 2 cylinders. If the motor just shut off, ur probably fine and just could have the head decked, and put a new head gasket in it. Everysingle time i've seen it, bad things have happened, i've seen cylinder competely split in two lol.

I could be wrong in this case. But everytime i've seen something hydro locked..that was the case, full of coolant. Good luck, with what ever the issue may be.