iPhone Says I Have No Music, Then It Says I Do?? Confused!

So last night I get into my car and plug in the iphone and it tells me there's no music on it, despite the fact that I currently have about 15 gigs of music on it. But according to the phone, I have none. No music, no playlists, nothing. The phone indicates that I still have only 3 free gigs, which tells me that the music is actually still on the phone, because if it somehow got deleted, I'd suddenly have an extra 15 available gigs, right? So it's on there, but the music player refuses to recognize it or allow me to access it, despite the fact that it's seen it all just fine for months and there's never been a problem before.

When I got back home I plugged the phone into the computer and loaded up itunes, which confirmed that yes, the music was all still on the phone. And yet even when plugged in, the phone still said I had no music. Just for grins I tried adding a new track to the phone, just to see if it would let me access it. When it finished syncing- it once again showed me all the music on the phone and would allow me to access and listen to it. 12 hours later and I can still see the music and access it, which is great.

Now everything's back to normal, but I can't help wondering- why did that happen? And will it happen again? What caused the phone to suddenly decide that I had no music and what made it change its mind and decide that I did? Should I be worried? Is this a sign that my iphone is dying? Or does this happen to everyone now and then and I just had no idea?

I'd really love to know if anyone else has had this problem or heard of this problem or has any thoughts on it, etc. Rest assured that any input anyone has would be greatly appreciated.

Much obliged!