ok now, she might have meant nothing, but she is a part of his past, and she is not just some random girl from the college but someone whom he dated, so is it really too hard to believe that he might remember a few details about her. I mean when I come face to face with my school frens, which by the way happens in years, and we get chatting we tend to remember so many things that we don't think about otherwise. I think its called something by association, in psychology wherein a slight thing, like seeing a person or a thing triggers a memory thats hidden somewhere. And I hope u know that our mind can never be formatted completely all the data that we think we have forgotten is still there and may surface from time to time.
Now secondly, about the eye lock, here let me refer to the scene where Arnav finally says to La that he cannot marry her and she asks him to hug her once. Now there Arnav was definitely clear about his feelings but did the hug feel mechanical? No. Because whatever it was between them, whatsover, it was something and again you may say it meant nothing but even a bond u share with ur pet means something right? And if they dated then at that point they might have had reason for it. I am not denying that Khushi is his only love, she is. But loving her doen't make him immune to every other person around. And then she is a single mother, Arnav probably understands her better than others around and so could sense that she might have been hurt by what mami had just said, and so that look of "I understand." to me it didn't seem like saying "Oh god! letting u go was a mistake. I still miss u. Lets get back together." but did it to you?
Finally the only thing I disliked about the episode was the pool-side scene with Arnav-Aarav-Khushi, I mean identical dikhane ki bhi hadd hoti hai, its getting silly now, and also that gum trick was way stupid, even for Khushi. But I guess the final scene between Arnav and Khushi made up for it, it was just perfect, both Baruna and Sanaya at their best once again.
PS: One humble request, can we please not call her Shit-all for now, the term is really derogatory and for now we don't even know what the reality of the situation is.