This does not sound like a gradebookj issue, if your quiz results are now gone from the Quiz interface.
If I understood you corerctly:
- There was one course where students took a quiz. Then instructor printed the gradebook that included quiz results.
-Instrucotr came back into the same course after some period of time, only to find that student quiz attempts are now gone?
It sounds like someone deleted the quiz results via the quiz interface, if they are not displayed in the quiz anymore (which would cause them to disappear from the gradebook as well)
Or, in case you had some upgrades/code changes during your "semester" - that could also influence things.