When my kids were little, we used to have hamsters and we enjoyed watching them a lot. They were always little escape artists and would be constantly looking for a way out of their cage. We had one hamster in an old-fashioned round-top bird cage, and it had the little latching door in the front that slid up and down. Naturally, a bird couldn't get out of that, but the hamster soon discovered it and learned how to slide the door up enough to wiggle under it and get out. We would put him in, and he would run right back to the door and climb out. When he had this down to a science; we turned the cage around, so the door was now against the wall, and the side where he had been escaping from now had NO door ! !
Well, that poor little fellow about went crazy, and had us all rolling around and laughing at him as he went back and forth, shaking every single bar on that side of the cage trying to find the lost door and get out. You could actually see the consternation in that little hamster face ----- he knew that door had to be there, and could not understand why he couldn't find it anymore.
We had such a great time watching him, and would do this every now and then, just because it was so much fun to watch the little Houdini Hamster trying to escape !