I had a similar experience with a young Black Milksnake that escaped,(because I was an idiot and didn't lock down her terrarium top after showing her to a friend). She was loose for six weeks in our house. We didn't know if she had escaped to the outside or not, but we would occasionally hear sounds of movement late at night. Then one day, exactly six weeks later, she showed up [i]back in her terrarium[i]! She, apparently, had been going back into her open terrarium to get water while she was loose. I fed her well that night, to re-enforce any memory she may have had of finding food there.
I've also had our large male Black "hide" from us when he's loose in the house, but he has always shown back up within a day or so. Right now he is hiding behind some stacked boxes underneath my computer desk.
Does anyone else out there let their snakes have free roam of their house like I do? I've only known of one other family that did this. When I was a kid,( in the '60's), I knew a guy that had a 6 foot California King that had free reign of the house. Even slept in his bed!
Mine doesn't sleep with us, but he is allowed to "stay out" over night sometimes.
Don't misunderstand me. He is usually put back into his terrarium each time we let him out, but not always.
In case you're interested, you can see our Blacks on youtube. Just type in RusellAllen55 to see some vids of them.
The photo is of Nina, the young female, just before she escaped. She's almost solid black now and much larger.