There are several things that can be done to monitor your surfing. Probably the easiest is to install a program on your workstation which will record all websites you visit.
Another thing that can be done is recording your internet movements on the office router, through which you probably connect.
I am sure there are other methods, and I wouldn't be surprized if your surfing was on record somewhere. Whether or not they'll bother to check or even care, you'd be able to answer better than I
