Although it is uncommon (or rare), vehicles disappear when you exit them.
First time this happened (about a week ago) with an ADA 4x4 when i stopped at a gas station and exited the vehicle, then it just disappeared.
I have a private server so i logged out and restarted the server, logged back in and it was back where i parked it.
Second time (12/24/19) i stopped at another gas station, i exited an Olga and it disappeared for about 2 seconds and reappeared back.
I have noticed that sometimes when i exit a vehicle it get a quick view of the space beneath the ground. It seems almost like when i exit and part of my character gets placed partially under the ground and catches a quick view of sky space and then gets re-positioned back above and on the floor.
Map: Chernarus