If it is on a concrete driveway, a hole can be drilled with a (rentable) hammer drill to drill into the concrete, and an anchor with a hardened ring can be placed for a chain/padlock to secure the camper. Different sizes of anchors are available.
You would have to figure out where on the TC would be the best/stoutest/most secure place of attachment.
On the issue of theft of truck campers. There is a slight up-side to states that require a truck camper license plate and therefore provides a title for your truck camper. There is a slight bit of comfort (possibly misplaced) in that you hold a title to your camper with the serial number on it. Unfortunately, if it is taken to a more common non-title state (Bill of sale only) it could exist and be used there with no questions raised since no bill of sale is required for a carried TC during a traffic stop (correct me if some states require that, please).
Interesting (?) aside:
I live in WA where both title/registration are issued for TCs and a current vehicle license plate is required to be displayed on the camper.
I was in Texas and pulled into a parking lot. A city police car followed me in, and when I stopped in the lot, he flipped on his lights behind me after I had already come to a complete stop. I have no idea how long he had been behind me, we were looking for a certain eating establishment among a bunch of other businesses to meet up with friends, and my attention had been on finding it.
The officer came up to my window and wanted to know why I was displaying two license plates on the rear of my vehicle, since that was illegal in Texas. I explained that it was required in WA, and both a title and registration was issued for the camper. I showed him both registrations (truck plus camper, fortunately both current) and explained that it was a small revenue stream for the state coffers.
The officer was very nice, but was scratching his head about the new concept of "two plates" displayed.