There was a ProSeries download last night (Form 8606 is now ready for e-filing, printing, etc.), so maybe your ProSeries closed down to upload the new files.  I know that it usually states that it will save the file when that happens so I don't know why it didn't save yours.  In the past I have had instances where ProSeries crashed and didn't save what I was working on, so I feel the pain.  I would try to remember to hit the save icon just in case when I would leave the computer, just to be sure.