I truly don't remember BF/F being there that night.
The word DEPRESSED comes up quite frequently. Depressed is not the word I would use. ANGRY yes, and embarrassed yes. At both herself and father. She spent the night at my house that night to cool off. Both SL and father acted, IMO, like asses but then I think alcohol was a big contributing factor. As for SL and alcohol? Can't be sure. Father yes. Big factor.
bbm: -- I think this is a really important piece. So I am jumping off your post and speculating -
Maybe the BF/F was invited and didn't show to the party? Maybe he showed up earlier and left or left after the incident? SL was understandably embarrassed by the drunken antics of her father, and I want to add humiliated (felt shamed) in front of her friends. --To me, that is potentially a really big deal. Here she is, a beautiful and accomplished college grad having adhered to the strict and disciplined lifestyle, and was a straight A student with musical honors, feeling humiliated in her own home.
I really feel for Sylvia here because ok, her father drank and she knew that but maybe what she did not expect was to feel humiliated in front of her friends. Or, maybe this wasnt the first time, either. Did these friends know her dad at Wagner?
IMO...Families are so imperfect and if we are lucky enough, and live long enough, there is hindsight and the coming to terms with our parents humanity or lack thereof. I think I was 40 when I sorted all this out.
So, on the evening of her disappearance, if one takes what the BF/F said about their argument in the car (at face value) and SL storming off in traffic (at stop sign, whatever) - and assuming the BF/F knows at least some details of Sylvias feelings about what was going on in her life, father, party, maybe in the heat of a mixed up argument, the BF/F told SL if you are so angry and you don't like it there's the door, etc... And, she bolted and he didn't expect that. -- Knowing she stayed with her girlfriend recently, it could explain why the BF/F went to MMQCs house, first.
I am not advocating for BF/F but to me, there are a lot of unknowns. --If he outright killed her, why is he telling anyone about an argument or her glasses? --Not a good alibi (imo). --Then, to be pulled together enough to make an appearance at two houses? Why not call on the telephone? Does the BF/F have any history of violence? And how does that reconcile with a happy, in love couple? Was there any violence in their relationship?
At the more innocent end of the spectrum, I do think the BF/F was not forthcoming with the whole story. If she left early and he didnt care until later, better to say fight was later, etc., make himself look better. Or, she gave the ring back stormed off and left her glasses better to not say anything about the ring, let her tell her parents
Dumb stuff like that.
I think it is possible she left and met up with foul play in another circumstance. That night, did Sylvia reach out to a lesser known contact or friend because she did not want to be found? Theres a group of friends at Wagner, or even mutual friends or contacts she met through the BF/F or someone else. She could have gotten on a ferry boat anytime day or night.