Plug of metal pushed out of the cylinder wall by a bolt

Had a lot of help off this site assembling my first Mopar small block. Had a friend helping me yesterday and as he was bolting on the timing chain cover he accidentally inserted a bolt that was too long in the bottom right portion of the timing chain cover. I heard a tink noise as I heard metal hit metal. A little small plug of metal from the #1 cylinder had fallen out and hit the support leg of the engine stand. Luckily it's below the bottom of the oil ring at the bottom of the stroke.
The motor is a 1971 casting .40 over. I would have thought the bolt would "bottom out" before this would ever happen. He said he had just started to feel like it was close to the bottom and it was just starting to pull up the timing cover when it happened. There's one thing for sure that I will never put a stroker kit in it now.
Anyone else ever have anything like this happen?