Revealing mistake: When Kyle gets to the past and hits the floor his body changes - even his hair and the sweat on it, showing the stuntman.
Revealing mistake: Just before the tanker blows up near the end, there is a scene of it turning to hit a vehicle. The cable pulling the truck is visible.
Revealing mistake: When the inner workings of the T-800's damaged arm are shown, he uses a vise grip to pull one of the finger control rods. As he does, the finger uncurls a split second before the rod is pushed back.
Answer: Gonna be totally honest... that might just be nothing more than a simple continuity error. They accidentally made a phonebook prop that didn't match up with the locations where they shot, and assumed most people wouldn't notice or care. (And to be even more honest, I never noticed it until I saw this question today.)
TedStixon