See Preview File Retention in Preferences for information on what files may be opened and how they got here.

When you click this button, you will see a standard Windows file open dialog. Unfortunately, the list of file names that you see is probably not enough information to figure out what report it is you want to see. On the file open toolbar, you should see an icon near the top of the dialog box called Views, and one of its options is "details." If you click on the details icon, you should be able to see a little more information about the files. You may click on the column headers to sort by those columns in any effort to fine the report you're looking for. Unfortunately, not much information is available to you here, so you'll just have to open as many reports as it takes to find the one you're after.