I once DID raise the 5th wheel without a battery in it, off the truck's idling engine/battery.
I had a pop-up camper stolen out of a fenced storage yard. Incidentally, be aware that such places take no financial responsibility for your loss. Keep the insurance in place. Even with the insurance, I was made only about 80% or so whole. And you can never think of everything that was in there . . . years later, we are still remembering things we lost that we couldn't think of when filling out the claim. The police said it was probably at the back of someone's property, being used as a hunting or fishing shack, never to hit the road again.
My 5th has a locking collar on the pin. It would be difficult to remove, but hardly impossible. It's probably the only such protected trailer in the fenced parking area. I figure far fewer people are equipped to steal a 5th wheel vs. a bumper pull trailer, but should someone choose to do it, hopefully they will go for a trailer that has no pinbox lock.