Um...

I just called the hotel to see if we had enough rooms blocked so they weren't released, and she told me who was booked. There's one name that I didn't recognize and they are not on the guest list.

Mystery solved! I called back, and it's my great aunt's caretaker who booked a separate room. Whew! That makes me feel better...I thought I had a really well prepared weddign crasher on my hands!