The car crashed and ruined then despawn.

One of 2 things could've/would've occurred, first, when you're still in the server as it goes down for a restart or crash(server crash), your character and whatever he's interacting with usually gets rolled back in time slightly, normally unnoticed while on foot, but if traveling at 50kmh, your Vic is usually a few hundred meters behind you on your traveled path. Secondly, and possibly more likely since you were playing on Official, the server went down while you were driving, you left/were kicked moments before the server actually goes down, and your Vic kept on keeping on..... and driving in official, with the complete lack of attention given by the devs to increasing the Vic's resistance to damage that wouldn't even dent a real Vic causing them to destroy themselves....it probably hit a chicken crossing the road at a measley 20kmh and blew up (joking, they still haven't returned lighting a match to the fuel to explode Vic's) and despawned. (Still probably destroyed itself going 20kmh, just wasn't in a glorious ball of fire and area destruction, just itself and your gear)