HI
We have been Storage Managers for 35 years at various facilities from Louisiana to Arizona with RV storage.
People will steal anything. They will steal the trailer, the batteries, the propane tank, the items in your storage hold or everything inside the coach or just break into the coach and have a party and ransack it.
Make sure nothing attractive is visible via windows.
Don't store you coach at the cheapest RV Yard in town unless you have checked the local police records to verify they have been crime free.
Our coach (knock on wood) we hope is the least attractive in the storage yard. Remember if a burglar wants in -- they will get in. You want your coach to NOT be the easy mark.
We have a quality tongue lock. so the entire trailer cannot be easily towed off.
Yes we have seen entire trailers stolen.
As for the batteries we did the $7 battery lock
NO, it isn't bullet proof but our goal is to make our coach -- the hardest one to steal from.
For the propane tanks
The two above youtube videos are easy and cheap.
We have our Toyhauler in covered parking. We opt to leave all of the blinds OPEN so people can see their are no valuables inside. We don't even have a TV as we camp to forgot society. I'd rather have a belt scuff on the outside from a curious looky-loo then pay for the cost of forced entry.
If you have valuables inside then you need to close every blind on the coach.
You can never protect your coach enough, the thief will get in...but you can make your coach more challenging than the other coaches and that will save you!