The Mr gave it away for me, but if you do say your name out like "Mr Whats Your Face", that isn't a common term like "Whats his face" and "Whats her face". You say those when describing someone else to somebody. For Example:
You: "Hey you remember ol Whats her face from San Diego"
Me: "Oh yeah she was dating Whats his face"
Whereas your name, would be like saying it to the person whos name you can't remember:
You: "Do you know what I'm talking about what's your face?"
Me: "Yeah, and the name is Crazzzy"
So when you look at your name the way you intended it reads "Mr Whats Your Face", whereas someone who reads it quickly, it looks like it would sound like "Mr Whats Her Face"
That's the only reason I can think of as to why people think your a girl
