TIFU by waving to a friend at the gym.

I was at the gym earlier tonight, doing my daily 2 miles on the treadmill when all of a sudden, someone I knew from high school walked in and got on the treadmill two to the right of me. It didn't seem like they noticed I was even there, and she was engrossed in whatever she was watching on her phone, so I just let it go, right? Nobody likes being disturbed while they're exercising. So, for the next half hour, we both continue running, her completely oblivious to my presence and me running the whole situation over in my mind. Should I wave, or something? Should I try to get her attention, even if just to establish that I am there and haven't been staying knowingly silent this entire time? Won't that be weird, since I've waited a full 15 minutes to start thinking about this? Should I pretend to have just noticed her there now?

I decided that the best course of action was that if she left before I did, I would leave it be, and if I left before her, I'd get her attention and wave on my way out. It'd be kind of funny because it'd point out subtly that I'd been there the whole time but she had never noticed, and knowing her, she probably would have laughed at the whole thing looking back.

I finished first, and got off my treadmill, sweating half from exertion and half from the social part of my mind telling me to interact, damnit, and as I was leaving, I waved to her and actually established eye contact for the first time.

Complete fucking stranger, never met her in my life, I'm a stupid dumb idiot. I had been 100% certain I knew this person, but it seemed it was just her clone, who had no memory of me. The worst part is that she was in fact a very pretty girl, so she probably gets awkward waves from plenty of guys she's never talked to, people I tend to spitefully call "creeps" and people everyone else likes to call "socially functioning males with any semblance of confidence".

She looked at me weird, and waved back with a sort of half-smirk. I walked briskly out, got in my car, and had a terrible drive home, worrying about pretty much everything and regretting ever leaving my house ever.

In other news, I've got a blister on my heel the size of medieval Europe due to lack of athletic footwear.

tl;dr I waved at someone I didn't know and got a weird look and now I can never go to that gym again.