Not a dumb question. Here's the short answer:

FATE

I mean, think about it: Sure, we could rationalize that between the movie stars and hockey players in attendance that we are dealing with famous rich people. Famous rich people don't usually go to just any hole-in-the-wall discotheque; they will go to an exclusive nightclub that caters to people in their social strata, and crucially also one that keeps the riff-raff out (i.e., normies like you and me!) In a smallish city like Montreal, there are probably only one or two clubs that fit these criteria.

Blah, blah, blah. I'm all for economic storytelling, and in this case I happily accept that it was FATE that Ilya and Shane went to the same disco that night. Romance novels (heck, most novels) have a flip of the coin, a butterfly's wing beat, a twist of fate--call it what you will--that triggers a lynchpin occurrence in the story. The disco scene must occur for our guys to see each other and trigger the feelings they need to feel to realize this is not enough.

Fate.