Why did all my songs disappear from my iPhone?

Strange! I had to check to make sure mine were still there! Did they get lost in your last sync somehow? Did you try to power off and back on to see if that resurrects them?

that is so weird!
my phone crashed before and i still have not reloaded my songs.
how strange, please let us know what happened when you fix it.

Are you syncing between multiple computers? If so, the sync for music and other media can only happen between one computer-a limitation (for technical and licensing reasons) of the iTunes software.

I would just resync with the original computer if a hard reset doesn’t work (hard reset is pressing and holding the sleep/wake button and the home button simultaneously until the Apple logo appears.)

(sorry-forgot to finish my thought)-if you are using more than one computer for sync, then make sure the settings for syncing music are unchecked on the computer that doesn’t hold your multimedia.

I use a MBP laptop for business and scheduling, and an iMac for my entertainment and multimedia. So for my setup, the laptop has the first tab (for address book, calendars, etc.) checked, and the rest of the tabs for music, photos, podcasts, etc., unchecked, and vice versa on the iMac.

Hope that helps.