Missing Audio track when I open a saved session?

[Dj A-Ron]

I opened up a session that I've been working on last night and a pop up window opens that says something like "There are missing audio tracks in your session" or somthing like that. There's also a window that opens that asks you is you want to try to find them or skip the search. I've never had this problem before. I did have an Audio Track that I had a Cymbal Roll on and that track is all of sudden GONE! When I do the search in the window that pops up, the workspace browser opens and I can't find the Audio Track with the Cymbal on it. All the other tracks in the session are Intrument tracks with MIDI. I'm guessing I just hit a weird button somwhere. Any suggestions?

PT 7.4
M Box 2
Core 2 Q6600 Quad core
2.4 Ghz
4GB RAM
320 GB sata
500 GB firewire for audio
Vista Ultimate