I had this happen to me back in the spring with one of my better climbers. I finally found him in my closet the next day. The poor thing I was heart broken. They are definitely hard to find especially when they are dried up so my suggestion is to get down on its level and search every corner starting at the enclosure. It is likely he went and took cover under/in something dark so check under and in everything. Especially your shoes before putting them on. I am very sorry you have had to go through this. Best of luck with the new guys.