recognition

I saw a girl on campus on Thursday that I recognized from my freshman year here. I think her name is/was Brittany. She worked behind the counter at Teryaki Stix. I would go there for lunch on most days, and she was there most days. Our exchanges went something like this.
Her - "Hi, can I take your order?"
Me - "Ya, I'd like a gioza bowl, please."
Her - "That will be (fill in price here)."
I hand her my dining plus card, she hands me a receipt and gioza bowl. "Thank you" and "Thanks" finish the deal.
On one of the last days of the Summer term, she struck up conversation more than the normal business transaction. She asked if I was staying for the coming semester, I said yes, and she gave me her number and said we should go do something some time.
This very much caught me off guard. I was barely 18, and I wondered, does this girl know I'm not older? I think shes at least 20, maybe I'm imagining that. I had a hard enough time asking out girls I knew, much less complete srangers. I never called her, and I didn't eat at Teryaki Stixs anymore.
I don't think she recognized me on Thursday. I remember her being taller, but then again it has been almost four and a half years. I'm 22 now. Maybe she shrunk.