almost the same happened to me years ago,,, when titles weren't so strick,, i wound buying another car same year for a few hundered bucks, then as i did take the dash apart and switch numbers and title the good car. junked the bad one. with no paper work you have two choices, 1. sign his name or junk the car,, oh if the co worker is being a ***** you can tell her that if you are driving the car and run over someone she as the as the inherit owner she is liable,,, but she may now list the car as stolen.. if i were you i would cut my loss and park it in the work parking lot and let her worry about it.. jim