During long recording session the computer stoped responding. I had to rebboot. I found the track but even though its size is 600MB the time in vegas is 0.
Is it possible to restore it?
Probably, but you'll almost certainly need to use a tool other than Vegas to recover the recorded audio.
The way to do it involves using an audio editor that can open the file in RAW mode - Sound Forge can do this and is what I would use, but many other audio editing programs can do this too.
Search the Sound Forge forum here for the word "RAW" and you'll find a number of posts from myself and others describing what you need to do.