We already know that Ted doesn't meet her AT the wedding.
This implies he meets her after it (opened up bow tie and all). And at night, so at the end of a day. So if season 9 takes place during one day of the wedding, he would meet her only in the last episode.
Yes, but we also know from "Band or DJ" that a week before the wedding, Ted arranges for her band to be at the wedding, and then we see a glimpse of Ted at the wedding, where he sees the Mother for the first time playing bass guitar.
He may not physically meet her/talk to her until later on that train platform, but he for sure sees her on stage.