I normally, just say "sorry, I'm taken", but I like yours much more.
Had a girl tell me something similar once.
The story:
I was walking passed her on my way out at the Fresno HNY and I had a rose with me that I haven't given to anyone that day. I handed it to her and told her that she deserved a rose to match beauty. My cousin rushed me off because we were leaving so I just left her with that line.
Couple of years later, I saw her again. A friend of mine took me to her house to visit her and I didn't remember her but she remembered me very clearly. By then, she had a boyfriend already. She said she's seen me around the soccer tournaments all the time, but I never came over to talk to her again. She said she used to dream of being with me because I was so nice to her when she needed it but she's currently got a fiancee and they were planning on getting married soon so we can only be friends. I never saw her again after that night.