It was an example that snakes can get internal scratches and they aren't bulletproof. It depends how sharp it is, hopefully the vet can take it out easily, my biggest worry is that by pulling it up you can scratch the internals, which is possible.
I did some more research and there are multiple cases of this happening with videos and pictures. So it has happened. However if this substrate has a sharp point then it could cause damage by pulling it back out. However I think it likely is substrate because cysts don't form overnight and it was directly after eating.