Sign of age?

So I was in the mall yesterday and I was going downstairs while this girl was going upstairs, as she passed by me she smiled and nodded at me, so I automatically smiled and nodded back. Just a few seconds later I realized I know her. But from where? The more I thought, the more I remembered her, flashes of her face came to my mind, the kind of clothes she wears came to my mind, the way she talks and smiles came to my mind. The only things that didn’t come to my mind were her name and from where I know her. Am I aging?