This is how I work. In more than 50 years of playing gigs, I have never had gear stolen. I don’t let it out of my sight unless someone I trust is watching it. If we go to eat after a gig I will only go to a restaurant that provides seating with a view of my parked car. If not, I drive on and eat later. I never leave gear in the car at home either. That is NEVER! My stuff will not be stolen.I don’t leave my basses/guitars unattended at gigs, and, if I have to step away, I ask a responsible band member to watch it for me.
Sorry for your loss!
P.S. Check with the cleaning crew.