what the hell?

I went tubing after school today with some friends, my parents are going to some concert and my brother is spending the night at a friends house so my grandma was supposed to babysit my sister until I got home
but she didn't expect me to be home until around 10:30pm
but I got home about 30 minutes ago (7:50pm)
there was an empty martini glass on the table
a coat that I didn't recognize hanging on a hook near the door,
two big glasses on the counter as well as a nearly empty bottle of Crown Royal and two empty cans of ginger ale
theres another martini glass next to the computer,
and the weirdest thing?
nobody's home
I really don't know what to think right now :S