That sucks. We leave most of the stuff in the TH when in for service. Since it's been out of warranty, any service I don't do is handled by a local dealer in our town. I'm on a first name basis with the service manager and service writer, trust their techs. So far no issues.
I always remove the following before leaving the trailer: passports, cash, any financial or confidential paperwork, network storage hard drive with backups and confidential information, motorcycle, helmets, kayaks, bicycles, Condor pit stop chock, bogie boards, tool bag, air compressor, Etc. We clean out the refrigerator, and take any clothes or other items we think we might need. As service is only 20 minutes away, we could run over if there was something we really needed.
I leave the two Apple TV boxes, Amazon Fire TV box, cable modem, Apple wi-fi router, and 3 TVs. While it would be annoying if they got stolen, those are all easily replaced. Have to balance risk/importance of loss with hassle of removing items.
2013 V 3105
2016 F350 King Ranch CC 6.7 diesel dually