Thanks, that's a huge help. I did some more digging (now I know what it's called) and found this TSB that shows were it goes in the case.
I couldn't believe that flimsy little clip would come from inside a trans, I was racking my brain trying to find where it came from. The good news is I don't have to take any more apart than I already have. The only tricky part now is getting the OD piston back in.