We had a Gunter since two days, fully equipped, all in pristine state, and a Olga with one doorsnd the good missing, but all in pristine state.
Yesterday we were 2 people in each car, driving around the map to loot industrial sites. We were driving quite a long way to the coast. Between Elektro and Cherno we had issues accessing the inventory of the cars (items couldn‘t be taken out) and decided to restart the server. After the restart, both cars were despawned.
We had that problem once after a friends game crash, but then we found the car back the way we came, crashed and smokind. This time we wentback all the way we came from on foot, couldn‘t find both cars.

Btw, we also had a Large Tent, it was set up, but empty. It despawned after a server restart