When I asked my now wife for her number the night we met I totally blanked on her name for like 15 seconds when I went to write it down. Thankfully (I think?) I remembered before she walked away.
I'd agree that honesty isn't the best policy here. I like the "who's this?" approach. You could also call some time when you think she'll be away from the phone or have it off, and hope she has her name on her voicemail.
Scott
