Strange. My friend blew up my Mesa three times 2 days ago, and I blew it up myself over twenty times 2 days ago and last night. Try checking in LS Customs for both Tracker and Insurance on the car from time to time. I heard that these can vanish sometimes.
Ya all 3 vehicles had trackers. It was questionable at first, but after the Voltic (a car that can only be bought & comes with a tracker) disappearance confirmed that this glitch swallows tracked & insured cars.
It's clearly because the bugs are nowhere close to being worked out of this game yet. My buddy who had $90,000,000 magically appear in his account 5 days ago suddenly had his entire online bank account double yesterday. It exactly doubled, to the dollar. That's a glitch. Now he's running around with something like $250,000,000. This game is f*cked.