I wish I knew. I reported in another thread that I've lost all mine as well.
Also lost my notes, my existing voicmails, my SMS messages, and my recent call history.
My calendar, photos, music and videos were not lost.
I'm stumped.
I've begun manually re-entering all my contacts, which is a pain in the ass as I had hundreds (although a good portion of those I no longer need).
It is EMBARRASSING to send a mass e-mail asking for phone numbers and addresses. I'm pissed at that. But I don't know if it was my error or Apple's.