I helped search for him today. I firmly believe he IS out there and wasn't taken by a hawk. The tree they have for him outside is a small sapling, only about 6 feet high that is a fair distance from the other trees. There were no damaged branches or leaves out of place or any blood or scrapes on the bark to infer a hawk had grabbed him while he was sunning. Seeing that a hawk would have had to come down low to the ground AND would have had to use enough force to pull him off the branches, I doubt a hawk came by. I've seen hawks attack bird nests before and they generally make quite the racket when they have to swoop in close like that.
I climbed a few trees, scanned the area, but it's a large area and he can be anywhere. I do think he may have seek shelter in the garage, which is relatively close to the tree. The garage is slightly warmer, has plenty of nummy bugs hiding around and many many vertical climbing surfaces. The trees, although their upper branches are dense, have trunks that are spaced fairly far apart, so he'd be crawling on the ground for a bit in hopes of finding a trunk that wasn't too slick to climb. The trees are mostly ash trees, which has a rather slick bark that might be hard for a cham to climb. I was able to climb up the ash trees, myself, but at times they were too slick for me to even grasp - and I've been able to climb up 25 foot bamboo stalks, no problem.
So I told her daughter to keep looking - I am sure he is out there, but now it's just a matter of finding him.