Bicycle detail

We live in a new apartment building downtown with a secure garage and a secure bike cage, or at least we thought. somehow the thieves got into the garage (probably followed someone in, and got into the bike cage (a bit more difficult). our bikes were locked together to a post with a combo cable lock. We thought this was enough with all the other security. Not so. I don't know when this theft occurred. the bike cage is in an area we don't frequent and we haven't used our bikes in months. This sounds strange, but it looks like my bike has been ridden. one of the tires isn't what I had on the bike and it's very dirty. it also has a long scrap on the top tube. my seat bag is also missing. very strange.