In GTA5 I upgraded Trevors truck during the campaign. I drove off to a mission in another car and when I returned I couldn't find it. I went to the safe house condo and to the garage up nothing has turned up. Could it be the vehicle impound cause the cops might have gotten it? Any help would be very appreciated.
The 3 characters each have a vehicle (Franklin also has a motorcycle). These vehicles cannot be impounded.
I have seen the vehicle re-spawn at the safehouse during an extended time on a single character.
You could try switching between characters (frequently when you switch back they are in or near their main vehicle) or sleeping to advance time and see if it comes back then.