Went from Scottrade to TD and now Schwab.
The entire time, I have had records of those CUSIPS in historical data (Schwab shows this in GainsKeeper), in their various forms (39ESC968, 939ESC992).
I have my release forms which show the original numbers (939322103, 939322814). Yes, I was a pre-holder before all this crap started. Since those of us who received shares following bankruptcy, went through the 12-1 conversion. etc., etc., I am not particularly worried about them finding us if/when we have funds due.