I monitor internet access and we have had a couple of people leave for regularly trying to visit adult sites. We make all our users sign an internet policy document though so they had broken their agreement.
If you haven't done anything though then you have nothing to fear, as someone from IT will probably go down the internet logs to see where you have been.
A pop up would only create one entry in the internet proxy logs which would originate from another site rather than the user's computer. Someone actually visiting a site creates many entries in the logs and can be traced.
i clicked on something once that i did not think was adult explict and my blocker came up adult content and i think i was a link for underwear on avon??