Thanks for the help guys and to Beat for the picture. That's her. I live in a small gated community, at the very end on a cul-de-sac and I've never worried about anyone going into my garage before. We usually don't leave the garage open much anyway, except when my girlfiend goes to work she'll leave it open since I usually leave 20-30 minutes after her. She does the same in the evenings.
But now there are two houses across the street from mine that are being gutted for Chinese drywall which results in a large group of construction workers showing up each morning. I suspect that one of them learned our schedule and grabbed the bike from the garage while I was still home but after my girlfriend left. Both of our bikes sit in front of her car and it would be difficult to get them out with her car there. Oddly, they left her Tassajara behind.