Music that was featured on a movie but never released

[Trinity Soul]

In previous films there have been featured songs that were never released, example music on Ant-Man a song was featured as a backtrack to the movie "Love Kelli - Our Time Now" I have searched everywhere and it is nowhere, another song is "Appogee - Tidal" (song is Tidal) (from Zathura) as well as music that was aavailable on Itunes for a short time but no one ever bothered to upload a version to the web like "The Weeknd - Simple Plan ft. Selena Gomez

If anyone knows good forum sites to ask others if they have these songs as well as other short run itunes songs that never hit youtube or anywhere else, please let me know