I did exactly the same thing early last December. The day before I had most of a day to be Amy, it was wonderful, and I was still feeling the glow the following morning when my wife suggested we go and do some Christmas shopping. All went well, and I enjoyed looking at the all the lovely party clothes for the women.
Naturally I had to use the facilities, and went to the location, looked at the signage, saw “Women’s”, and calmly walked in. Two things happened at almost the same time. I realized there weren’t any urinals, and a woman was washing her hands. I immediately turned around and made it out before I was noticed!
We call it the Pink Fog, and I suppose you were as deep in it as I was that day!