I am just seeing this. I am so sorry. My heart just breaks for you, especially since you are not even in the area now. Someone mentioned Disney, but lack of cameras does not sound like Disney to me...nor does the kind of treatment you are receiving. It's hard to say whether it's negligence, stupidity, outright theft or a combination.
I am not trusting of hotels/motels since I stayed in one one night many years ago and after spending the day out, came back to find someone else in the room!
We found our things in the housekeeping area but we put up a sink to get that help. Since we had rented the room for multiple days, we have no idea why they rented it out to another family, but the motel never gave a thought to stuff being left in the room as an indication that it was rented out already either.
I hope Benji is found quickly.