I remember searching high and low for the music featured in the trailer for The English Patient, later to learn it was Randall Meyers' music from The Telegraphist.
I remember being "fooled" at least a couple of times in the 1990s. I hadn't heard or seen Glory yet when I first saw the Backdraft trailer and James Horner's music led me to thinking, "I need to check out this Zimmer guy!"
And being ignorant of Kilar, I was very impressed with John Williams' new "sound" for Schindler's List.
Who else remembers the extensive search for the "mystery music" in the DOCTOR ZHIVAGO trailer? There was endless speculation about the piece and who might have written it. At long last someone identified it as a piece by Laurie Johnson entitled "Bold Horizons." It was used in an NFL film.