iTunes has deleted all of my music

Preliminary: I use Windows 10 and iTunes 12.3.0.44

Last night, after having iTunes uninstalled for some time, I decided it's about time to reinstall it. After reinstalling, it starts doing its usual "syncing" and "backing-up", at which point I go to bed. Anyways, I wake up this morning to find that my iPhone 4S now has literally no music on it, apart from a couple of iTunes pre-installed songs. Besides this, all that is left in my music is some of my Voice Memos..., and even for the most part they are gone!

My music was not purchased from iTunes, but this should certainly not be a problem as iTunes is not the only music outlet. Even if iTunes dislikes the fact that music was not purchased from them, that does not give them the rights to delete all of my files without my consent.

I have truly lost a lot of respect for Apple right now and would appreciate anyone's advice, as I desperately want to find where my songs have disappeared to. The iPhone had accumulated around about 500 of my favorite songs over the years, and I think it is crazy that these are suddenly deleted. There is no way I am going to be able to recollect each of the songs and return them on my own. I did not back up the files as I never thought iTunes would do something like this. Is there a contact number I can call, because honestly there has to be some traces of my files left somewhere; and if not, I certainly am not buying another Apple product and will certainly advise everyone to uninstall and never return to iTunes.

Thanks guys, I would really appreciate it.