Junior's got the answer. If there's a hole, you'll know it by zero compression in that cylinder or with a leakdown with a very high loss. Another thing to consider if you think you've damaged something is you could have wiped out your rings. Pre-det could blow a hole in your rings giving a similar result.

Buuuuuuttttttttt, why do you think you have a hole in the piston? Do you feel the engine missing on a cylinder or are you blowing smoke out the exhaust? Do you have a lot of crankcase pressure (oil or air blowing out your breather cap)? Your timing is a little high, but if you didn't stomp on it and let it ping itself to death, you should be okay. Focus on the fuel / cam / timing chain to get the timing to a more reasonable level. If you're a tooth off on your chain and gears, the engine may still run, but you may have to adjust the timing to get it to idle.

When you say new "stock" pistons, what does that mean? Cast or Forged? Forged can withstand more abuse and are not likely to be damanged by a few miles of pre-det. Cast may get pitted quicker, but in a hundred miles, it would be hard to say they are burned up. Advance in your timing doesn't burn a hole...premature detonation or a super lean mixture of fuel burnes the holes. Like if you use heavy nitrous with a weak fuel charge. Doesn't sound like you did any of that...yet!