Recently, one of my students was working in Pro Tools 8, and when she attempted to save her session Pro Tools flashed this ominous message: "could not save as because volume not found(-35)". So here is how we solved the issue.
The first thing that we confirmed was that the clip in question that Pro Tools claimed it could not link to, was playable on the timeline and in the clip regions list. Yet as hard as we tried, we could not get PT to re-link to the original clip volume (content, not volume as in loudness).
What that meant was that our PT session was playing from a cache and not from the original file!
But we still needed to save the session and not sacrifice all of the work done to that point. I researched it on the web, but none of the posted answers were positive. They pretty much all involved drastic measures or re-installs, and none addressed how to save the most recent work.
I came up with a rather straight forward solution. We changed the output of the track containing the bad clip to an unused bus. We then created a new track, with that bus as the input. It was then a simple matter of arming the new track, solo-ing the bad track, and then re-recording the bad section (containing the clip) onto our new track!
That created a brand new recording, and thus a brand new clip whose volume Pro Tools recognized.
The final step was to fully delete the original bad clip from the session and the clips region.
Problem solved; and Pro Tools was now able and willing to SAVE the session.