Don't say anything is what I would do in a situation like that.
Before I came out (long time ago) I had posted a pic to a site some of my co workers visited.
The pic was up for 2 to 3 seconds before I deleted it.
One guy sent me an email and asked if that was me in that pic.
I said what pic? He said it looked like you in womens clothes. I said really I never saw it.
He went on talking about something else and nothing was ever said about it from that point on.
Now if you start making excuses and trying to talk your way out then everyone will know you were in feminine attire.