Buying all cars unlocked it for me.
Got this myself. Unlocked the Ferrari Tributo, decided I wanted to have it in my main area and put my existing Aston Martin somewhere else.
Went to the Aston and selected "Remove Car", assuming it would put it in a safe place, went to Bay 1 to select the Ferrari and found both cars had completely disappeared. Can't even re-unlock them.
I'm assuming the only way to fix this would be to reset my save, but I'm scared of losing other stuff now to be honest. I haven't started a career yet, just afraid of losing pitcoins and Champions Edition benefits, because if THIS can happen, then...
Buying all cars unlocked it for me.
