I read a story online where a guy had an extremely similar situation with a YZ125.

Piston broke same place, top of piston looked the same etc. He fished busted pieces out, then with the engine out, he 2 cycle gas in the case, swooshed it around and dumped it out upside down. He did this maybe 3 times and he rebuilt and runs the bike again.

Anybody think this would work? By the size of the chunk I fetched out, there is very small pieces left. I did get a few almost shavings out with a rag.