Timing being so important, I'm surprised you would want to leave it to chance. Even if you're just moderately into racing, timing is so important, you should get the tools and make sure it's where you think it is. Or get somebody to do it. It can't cost that much to check the timing.
I doubt the piston was weak. It's more likely that you had the air/fuel mixture wrong. And of course, if the timing was wrong, (too advanced) that would just make things worse.
Do you know how many cc's in the combustion chamber? Is it possible that the engine might have been modified? Too much compression, with all the other problems, could cause the piston meltdown.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)