I realized that sound was a huge factor in getting me excited about the movie. It's a bummer that the sound design was so much more conservative / predictable than one would think from that trailer!
It's common to hear sound effects or music (score) in trailers that isn't in the actual movie or part of the movie's score. I liked the music in the final trailer for The Dark Knight Rises (I think it was the final trailer, at least the final US trailer), but it was never part of the actual movie or included when purchasing the movie's soundtrack/score. That sound effect in the IT trailer was probably just made for the trailer/marketing. Actually, it kind of sounded like a sound effect I heard before (not sure where though) but was mixed with a few other sound effects and kind of a "remixed" version of a sound effect I heard before.
Yeah, I've came across that sometimes. But then there is the Power Rangers movie. Trailers used some lame Kanye West song. The song was also in the movie. I hate Kanye West. I like rap though. I actually like ALL genres. It just comes down to the artist that I like/dislike.