This happened when I reported for my 1st reservist training, a few years after my active service ended.
After getting past the guardroom, I needed to report to my unit. I was unable to locate the unit as I was not familiar with the camp compound. The buildings all looked the same. Then I saw a soldier in front of me. I decided to ask him for directions. It was at this time that I noticed that the back of his hair was almost touching the collar, and the side of his hair already touching the ears. It is an unacceptable hair length. I thought to myself, this guy is going to be scolded if the sergeant major sees him.
I called up to him to ask for directions. When he turned around, I realized it was a female soldier. I was so embarrassed by my mistake that I quickly left after getting the directions to my unit.