Snipped- Very interesting. I do have a question for you, because I can't remember if you mentioned it in the beginning. Do you happen to remember if anyone else was nearby when you had this encounter? I'm curious if someone from IGA could have potentially noticed the car or the guy you ran into talking to you. If not, it makes me wonder if he attempted to talk to anyone else at IGA.
I'm thinking along the lines of someone who wasn't familiar with DS (if she was targeted) trying to find her at IGA to bring her back to someone so they wouldn't risk being seen.
Another thought, if LE is going a different direction due to DNA evidence not panning out, maybe this was completely random and it was just some creep targeting women at the IGA. Maybe DS would have been more likely to talk to a stranger and try to help. LE doesn't think DS drove the vehicle, but unless they have some solid witnesses/video placing someone else driving her vehicle, then I think the possibility that DS at least initially made it to the apt. can't be ruled out. I think it's quite possible she drove in and then someone met/grabbed her at IGA and decided to take her out in her vehicle to avoid contaminating their own.
Also, you mentioned you thought it might be a rental. Did you happen to notice any barcodes on the windows? Or maybe what make and model the car was?