It doesn't matter whether or not you leave credits for the song.
If Youtube's Processing protocol detects any music (by actually playing back the audio to what it has on their servers) that their database has listed as copyright protected music, then it'll automatically disable it.
You can get it back if you feel like it's fair use and you credited the artist. I had to do that with one (now removed because I didn't like it) video where I used a Hans Zimmer track from the Dark Knight.
