Sorry to hear this Becky.. same thing almost happened to me. last week i was pairing up breeders, cleaning ect. I left the room and came back a little over an hour later. I glanced over at one thermometer and saw it was reading 87 I was a bit confused as I have my Johnson controller set for 82 and it has been extremely reliable..
I glance over at the Johnson controller and it is reading 78* and powered on!! I was thinking what the.heck!? ... then I realized, i must have knocked the probe and it was lying on the floor!!! I was extremely lucky to have reentered the snake room by chance otherwise,... i probably would have lost everything.
I learned from the experience though, The probe is know securely fastened in place and I also installed a fan to circulate the air in the room so it is pretty consistent at floor and ceiling level. Also, I purchased a couple of meat thermometers at Target, they have an alarm that you can set to go off at any temp you would like. I placed two of these in my snake room and set the alarm temp to 86* I tested it out and it works great. I also got a baby monitor and place it in my snake room and I have the monitor in our family room. My snake room is on another level of the house so this set up will alert us promptly.
I am also going to do the same with my incubator which is in our basement.
Again I am sorry for your loss, thankfully though you did not suffer more loss.