In this episode Ted says that his future wife was there that night. We see her with the yellow umbrella in the beginning of the scene right after the opening credits. Later in this episode half way through, Ted is walking through the club and bumps into a girl, apologizes, she says its alright and then he returns to the girl he was hanging out with that night(the married one). I thinks thats the mother. There is no reason for the directors to show Ted bumping into some random girl, except for the fact for it is his future wife. Later in the episode when Ted is talking as the narrator he says something along the lines of, "I am glad I didn't mean your mother that night because I don't think she would have liked me very much." The irony of all of it would be huge! Directors try and hide things like this all the time, so it is definitely possible. Also, when comparing the outfits they are both wearing jeans when you see her with the yellow umbrella, and bumping into Ted. What do you think? I am new to this forum, but this has been my theory for a while now.

Meet Heather Riley. Cast as "Attractive Brunette," and the eventual Mr. Ted Mosbey.
http://www.imdb.com/name/nm1320856/mediaindex