If I'm in a hotel room, and something has dead alkalines, I'll toss the batteries, and try to make it very obvious the batteries were removed so they can be replaced for the next guest. That's not theft. I really can't imagine anyone stealing batteries.
I've never taken a remote, but I do sometimes find a hotel keycard in my luggage when I get home. I stay at the same hotels, so I tend to return them, although sometimes a few months later. Small items like that tend to be misplaced or lost by absentminded guests (and possibly even employees). I can't imagine anyone taking a remote on purpose. What would be the point? Most are specific to a given TV model, and wouldn't even work with a TV back home.
There is natural shrinkage which happens everywhere (especially my sock drawer). If someone takes a mattress, coffee machine, or towel, that's theft. If someone tosses dead batteries or misplaces a small item, calling that theft just seems mean. It's attributing bad intentions to something which is just part of life.