It seems as though you and the other user were both inside each other when you both left the company. This resulted in you both being in ghost mode. I believe on the other users game, you both separated so you were no longer in ghost mode for that user. But your game still thought you were inside of each other, so the other user was still in ghost mode for you. Which is why when you drove through the user it caused them to flip.
Short answer: They was in ghost mode for you, but you wasn't in ghost mode for them.