And they are using NFC for that?

Yeah, no one would just cut the label out, right?

Engadget had a basic article from a few years ago. I'm not sure how the alarm works as even the distance from the floor to your suitcase might be too far for RFID:

http://www.engadget.com/2011/04/20/that-hotel-towel-youre-st...

Inventory control does not necessarily have anything to do with theft. "Inventory management" would probably be a better term.

Which is the same as if a non RFID'd towel is missing from the room.

Er, no. Have you been to a hotel? They don't normally give you a single towel for your entire stay. The hotel changes the towels every day. Bulk RFID scanning during laundry lets them keep track of how many towels have gone wandering and individually track how many times specific towels have been laundered, which is probably useful information for managing towel quantities in bulk. I don't think tracking down and identifying individual towel thiefs is generally the idea, though I guess you can detect towels in places they are not meant to be (such as in their suitcases on the way out of the lobby).

This doesn't prevent someone from just taking a pool towel to their room and then putting it in their suitcase.