Hmmmm. It gets much more difficult to troubleshoot without this info - I'm a bit perplexed as to why it's not there. I don't think this file will be hidden by most systems by extension, but it's possible. You probably did a search, though, which should find it. By default, it's in the c:\Program Files\Ping Plotter directory. Can you do a quick manual review of that directory (preferrably by opening a command prompt and doing a "dir" there)?
If no .rip file appears, then can you save some data (File -> Save Sample Set) and email that to firstname.lastname@example.org
? Maybe something in that will give us a clue. Also, before you save it, can you mark the general time period where you got the error (or errors, if there was more than one). To do this, right-click on the time-graph at the point where the error happened and select the "Create Comment" command from the menu, then enter some description.