I have this set-up in most cages, a hide, a hide made of a plastic cup, a vine, water bowel and tree. I have the tree in most cages and it's scared me a few times.
Albie vanished from my cage one time, i pulled everything out and cleaned the aspen out and everything..i could not find Albie anywhere. I finally noticed that on the bottom of the tree there is a hole where he got into somehow. took me awhile to get him out, had to use a pinkie to lure him out haha.
Bandit (who's no longer with us) was coiled up on one of the branches one time when i took everything out of the cage to clean it. i looked in the hole and couldn't see him so i set the tree on the table and started looking around on the floor, behind the bookshelf, movie shelves, tv, under the couch etc etc etc etc....finally i thought he was just gone...so i continued to clean the cage and to look for him more once i got it all back in and when i grabbed the tree off the table to put it back i noticed little bandit coiled up on one of the branches...i had a pretty good laugh on that one..
Now all my trees are stuffed with paper towels so they can't get in the hole.
This picture is taken of the cage Dorky is in right now...if you notice the tape strips on the bottom right of the cage on the vent thing that is where Dorky got into because it used to always pop open when closing and opening the cage, i thought i lost him as well, took me awhile to find him in there..never thought of looking.