Here is yet another solution for the lost reports in the 2013 upgrade from another thread:
"Lost saved reports?? I had the same problem after I upgraded to Q13, but I figured out a possible solution. Open the report, at the blank page, and click on the Customize link upper right side. Under the Display tab, notice if any of the options are checked under the "Show Columns" menu option. If not, check as many as you need. This should display the original report with all the original customizations. I worked for me. Apparently the Q upgrade cleared the Show Columns fields in some saved report. Hope this works for you. I found nothing useful on the boards here. "