Disappearing cars

Is there a reason the technicals with the 50 cals disappear or is it a bug?
I was just doing some testing on farmhouse local play (no ai on map) and left the car for a minute, and when i came back it had disappeared.

This happens in all modes but until now there was a chance someone had stolen the vehicle and driven off but now i can confirm that they can actually just disappear, why is this?

The vehicle despawns after certain period of inactivity if it is activated at least once. It'll be respawned when next spawn wave occurs.

Not only that but noticed a few times where a npc is invincible. Shot him with all bullets in pointblank range. Either disappear or invincible.

@Arc So in push if the vehicle disappears or is destroyed, it will only randomly spawn again and very rarely. Is this also intentional?