It happens to the best of us. We have had about 4 or 5 escapees in the past few years. A small yearling king snake was out for 4 months. I had totally written him off. One day he turned up in the rodent room (surprise surprise). Very ticked off and dehydrated but alive none the less!
Another, we have no idea how he was out for nearly 6 months are we didn't spot him. We have mostly dark furniture, no basement and this guy was a 960 gram bright orange amel! Just turned up one day cruising across the floor when the cat spotted it.
Actually, all except one (I think) was found by our pesky cat. I guess she is good for something after all!
Glad you found your escapee, but don't beat yourself up about it. Corns are escape artists and it happens to all of us from time to time.
Q