
Maybe .... I think for brief he just forgot but then he realised it and ran away. Or maybe Becoz he brought her in and was scared Wat happened to her he must have been lost in thoughts and later wen he realised the maid removed her dress ... so he ran away(〜 ̄△ ̄)〜 I think I m using too much brain cells( ̄∇ ̄")

well, that's just what I thought, and you guys' thoughts seemed reasonable too. (≧∀≦)
Anyway, I'm intrigued by that part that it was already implied before. It looks like I've forgotten or missed that part in the story which chapter was it? lol.
On another note, if he truly knew from the beginning then I think that the creator/author is quite creative in terms of deceiving people and at the same time adding hints about that matter that was almost nonexistent to the point that if people don't pay attention to it no one would notice.
you know, I've read ch 31, and since their deal took place his highness has been referring to our MC as HER in his inner dialogue. I don't know if it's because the original word used can be translated to anything depending on the context or if it was the translator's preference but if neither was the case and he's intentionally using HER to refer to the MC while in the general's knowledge he's supposed to be a man in his eyes.... I just think that he actually knows that HE was actually a WOMAN. His romantic actions didn't seem like they're only for show and ch 31's first part kind'a show a little sneak peek in His Highness's thoughts.