Sad to read this thread.
We travel rather spartan by design, usually not with anything we don't want to lose, but we've never had anyone lift anything from us.
Thieves tend to be opportunists, and I always do my best to make it difficult for thieves to pack off with stuff. For example, we travel with our two bicycles. During the day, we usually keep them parked somewhere alongside the coach, but at nighttime, I wheel the bikes around the backside of the coach and chain them together. They are still outside, but it would be a real hassle for a thief to pack off with them.