I don't know if this would even be worth trying now since she has been gone for a few weeks now, but has anyone tried walking her dog around the property and see if it like follows a scent or something.
The reason I bring it up is my dog, Trixie (yes, that sneeky looking puppy in my avatar pic), is overly attached to my best friend. It is bad enough that when he goes back to his home on the weekends, she pouts and watches devotedly at the sliding glass door to the balcony for him to return. She sniffs the parking lot trying to find his car. She even tries to pull me down to his apartment when I am trying to walk her around the apartment complex. She sniffs his trail, for lack of a better description, and has even escaped the apartment to try and track him to another friend's apartment on a few occasions (Yes, I know she has issues, but it could be worse, it could be someone I don't like, ya know?)
I guess I am thinking that her dog may have been as devoted to her as my lil bit is to my friend, and maybe her dog would try to follow after her scent, or maybe even if it saw what happened (which from the sounds of the behavior Rita has described, I would bet money it did) it would try to trace her last steps/movements.
Like I said, it is probably a long shot, but I see how Trixie does my friend, and I think "Maybe so...."