Congratulations! I had a very similar thing happen to the analog board on a Plus a little while ago: viewtopic.php?f=3&t=22279

That daughter board probably has the 128K ROM (from the Mac 512Ke and Mac Plus), which includes SCSI support. I had one of those a few years ago - I think it plugged into the ROM sockets or had a CPU clip... I can't remember now.