Guy's Behavior

I (F15) was approached by a guy (M16?) at school and asked me to be his "pretend girlfriend"?

I don't really know what to put as the title because there's are multiple parts to this.

I was walking the track at school during the break and a random guy approached me, we walked together and we were talking. He kept asking questions about myself (non-creepy), and when we had to go back to class, he asked me if I had a boyfriend and if I could be his "pretend girlfriend" so he could impress his friends, I said sure.

After school he approached me again and asked where he could meet me at lunch the next day. During lunch the next day I saw him walk by and look at me but never approached me, which I don't blame him because I have a big friend group.

I'm confused because he hasn't approached me since, I'm pretty sure he keeps looking at me but I don't know if I'm just imagining it. Why would he seem interested one day and then after that disinterested? Maybe it was a dare? Advice would be helpful.

TLDR: Guy approached me, asked me to be his pretend girlfriend, asked to meet me at lunch the next day, showed up but didn't approach me.
I (F15) was approached by a guy (M16?) at school and asked me to be his "pretend girlfriend"?
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