I have had it happen once but i can't remember why nor can i recreate it (a good thing). I would recommend the next time it happens to him he keeps track of exactly what he was doing that triggered it. Perhaps there is some bug with a certain step that triggers a quote to disappear i believe it may have been with previewing the quote before it was completed but wasn't saved and when you wanted to back out to go back to the quote you clicked the wrong thing like "x-ing out a window" by accident or something similar causing it to cancel the quote rather than go back into it to continue working. I would recommend saving before previewing if you are still working on it.