I forgot to post about this earlier. So I'll do it now. As the siphon brought the pond level lower and lower we started to see a catfish trolling the surface. It looked like it was eating algae. I tried catching it with bait and with a bait casting net. I threw the net right over it once and felt it in the net but it wasn't there when I pulled it up. When the pond level was down to about a foot we found it dead. Then later in the day we found the other one. Here's a pic of the first one:

This guy only had one eye....just skin over the spot where the other eye should have been.
The last time the pond was stocked was 20 or so years ago, a little bit before my grandfather died. Do CC live that long? Or would these be remants of a one-time spawn a while back? Also, would this mean I DIDN'T have a DO-crash-induced fish kill?
I'm letting the pond refill now, assuming that I killed all the BG with lime. We'll see if that's true. I would still like to know if it's normal for BG to die and Gambusia minnows to survive a lime treatment like that. Does anyone know?