So I was playing earlier tonight and went to pick up a special import/export car that Simeon wanted.
After getting it resprayed, I was on my way to his garage when someone started coming after me. They killed me and took the car, and I gave chase. I killed them back and went looking for the car.
I was at the green car icon but could not see anything there. At first I thought it was on top of the building or something, but as I ran I felt an invisible barrier and heard that metal clanging sound. So I pressed triangle and lo and behold, I 'entered' the 'car'.
The car seemed to be completely invisible. All I could see was my character in the seated driving position. As I drove along, I could fit through gaps that the car would not normally go through, so I suspect the dimensions weren't all there.
Has anyone else experienced this? Was this some sort of glitch that the other player who stole the car did? Or was it just a natural CPU glitch?