As Attie says, we here in Australia don't have these chemically treated scollops...Not that I am aware of anyway.
The only scollops I have even seen that do not have the roe attached, are packet frozen ones. I also think it is normal and common here to get scollops still in the shell.
So I can only guess to an answer, because I have never cooked chemically treated scollops. But my educated guess is the SS pan. Stainless steel really is not very good at all for cooking. I would suggest using a heavy cast iron pan. Or as a second best, carbon steel wok.
Even with copper ply, I just can't see in my mind SS staying hot enough for hot fast cooking. I think that is the problem.
I hope that is of help