Here's the deal. I was glass bedding an action, and got a bit of shmutz in the bolt stop. I was able to push the release in with my finger, and release the bolt, but it wouldn't pop back out. So I reached in & tried to pry it out with a small screwdriver. The little tab, you push on with your finger, just popped off. It must be pretty hard, and I suppose a bit brittle.
As to why I can't go through the usual sources, Remington lists this as a restricted part. I suppose because it is attached to the trigger. Doesn't make sense to me, but they didn't ask me for my opinion. So... Big Green, their repair centers, Brownells, and Gun Parts Corp., are out.
I made a new tab today, out of a piece of utility knife blade, and soft-soldered it on. It will work until I can find a replacement piece.
I don't remember ever having this much trouble getting a $3 part (remington's price)! but, THAT'S WHAT I GET FOR BEING HAM-HANDED. I know better, but just didn't think! Later, and Thanks,,,,,,,,,,,,,,,,,Bug.