Can you post a pic? That will help with ideas on how to remove. Definitely do not try pry them apart
So your lfs glued that scallop to the shell? I would stop going there.
I'm not familar with scallops---do they have byssal threads, and is it possible the store did NOT glue it, but that the creature attached itself? If they do what clams do, it's a natural adhesion that should not be messed with. But I do not know scallops. I THINK they're free-ranging, no threads.
On a side note they are nearly impossible to keep long term, better left in the ocean.