I was using foil tape to secure it, but I think one of the tubs bumped the probe, or maybe the probe wire got tugged on by one of my cats or something, but the tape that was securing it was ripped.

I'm going to set the ranco a couple of degrees warmer and put its probe on a different level, and then plug the herpstat into the ranco. This way if I had what happened here happen, the ranco would have turned off the herpstat and shut down the power.