Going Blank on Stage

Odd dreams in the last few nights or so. I do remember one night vividly. I was in a crowd, watching my favorite band perform (PSB). I was in the front, moving along with the music. Then the lead singer, whom I worship, pulls me up on stage, and we start singing along together. Hah! What an indulgent fantasy.
He goes to the microphone and says 'this lady is going to sing our next piece for us!' and I was so excited. I got the microphone, sang the first two words of the song after the long electronic buildup...then went blank.
The music stopped, the audience went silent. I just stood there. "Um..." Then I say something stupid 'Guess I don't know this one!' and hand it over back to the lead singer, and trudge myself off stage.
I was so embarrassed. How could I forget that song? I NEVER forget their songs! I've been singing it since I was 16, what is my malfunction?
I woke up with the biggest feeling of humiliation.

I wonder what this all means.