Missing Audio

can anyone please take the time to explain how i can find the audio that was previously in my session. i've been recording on this session for sometime and while laying down some vocals, i got an DAE error and it refused to play the song further. though if i started the track from the beginning, it'd play up until the point in question.

so i decided to save and shut down my session to see if restarting my computer would fix it, but now a guitar track i recorded several weeks ago, the session can't find when starting!? when i select to skip finding the audio file, during the start up of the session, my whole session opens and appears to be there execpt for the light blue spaces where the guitar audio used to be and was while i was playing it back to record my vocal audio. and the vocals i was recording tonight and the guitar from weeks past, were on two separate tracks. i'm having the search on pro tools search for it and it can't find it! how do they just disappear? this kind of crap shouldn't be happening on a top of the line program! please help.

dual 800 G4
OS9.2.2
pro tools LE

thank you to anyone who can help.

[mon]

well dude!!! it happened to me before!!!
.... so what's the possible explanation:
1. accidentally deleeted those tracks during organization (removing regions, disk allocating, or DURING OPERATION)
2. the worst, audio data must have been corrupted!!!! some audio data you are working and are recognized by mac but wont work at some point means an issue!!!!

*bits of advice: try to be organized from the start and backup or try to use backup softwares to automatically do the backup for you.