not necessarily oneitis, just a curiosity about a specific person who seemed notable or interesting to you. there was this really unique looking brunette at my HS who is a couple years older than me and just graduated this year. I don't really know what it is about her appearance that makes her stand out, she just does. I honestly can't list any distinctive features she has but if you saw her you would know what I'm talking about
she literally does not know I exist but whenever I saw her in public I'd think to myself 'hey it's that girl again'. I saw her at In-N-Out once but didn't make any attempt to talk to her. later I ended up next to her in line when we were filing out our AP exams, but I still didn't have the courage to talk to her. I figured I'd just end up humiliating myself and making her uncomfortable. which is probably true, so maybe it's for the best that I never had any interactions with her. to this day I still don't actually know what her name is