The grades were never accepted. You will need to re-enter them.
The problem is that this is not for just one class. It is for a bunch of courses random assignments and students. Not an easy solution when you have 700+courses for this semester. I am finding that if you unenrol the student from our DB synch (i.e. remove the student from the course) and then add them manually, some or most of the grades show up (so they are stored somewhere).
There still has to be a way to run a report or identify these disprepancies in what is in the grade history and matching it with what has not been updated/posted in the gradebook report. Very frustrating to say the least. This is like asking someone to keep the money with you but then the balances and/or transactions either do not match or are completely missing.
Hey Sal, had the same problem with one course of about 300 people. There is a Moodle Tracker bug report out there (can't find it now).
But yes, the grades are still in the database, just getting dropped from grade book. So, if we could find a Moodle database wiz, I might guess that there is a database field that could be updated. Don't know for sure.
I ended up doing a manual enrol for the students with missing grades. Unfortunately, the Restore Grades function only works for manual enrol, not for CSV upload.