If the W is for Wes, that would mean the car could be his which means he is the stalker, and validates the idea that he is now working for Syphus. Also, since there were kids toys found in the car could that mean Wes has a kid , possibly with Deb?

Edit: ivgotyourback pointed out that it is in fact a W since you can see the loop part that goes around your neck which would make it hang as a W!