Sorry, Sidelatch, you are right; I didn't look closely enough.
I really see no way to get out of that except to sacrifice the sideplate, or at least the end tab. Gun Parts Corp (
www.gunpartscorp.com) shows them available at $24.15 plus S&H. Getting a match might be hard, but if you send them some info and pics of the gun they might have the correct one. You will still have to fix the frame, of course.
I don't believe soaking in oil is going to help; the sideplate is not rusted in, it is jammed in place.
On further consideration, and since the sideplate is botched up anyway, try this: The sideplate is slotted into the frame only at the front and back, not at the bottom, and it abuts (is not under) the slide. So it MIGHT be possible to pry the sideplate out in the back, bending it so it can be pulled out at the front. I think that might get it out, but whether it could be salvaged is another question.
Jim