Looking at the very blurred furry looking blotch, to me, who is familiar with cats, it look like a cat standing on its hind legs up against the crib bars.
Actually looks like a squirrel tail with the large blotch on the bottom, but that I would doubt, but not entirely rule out. But I wonder if they have a pet cat?
If there is a video available, then maybe there might be a better indication of what it could be (an arm) because of any movement. But I don't really know why they would think it is an arm and not have some other ideas - such as mine