I was able to reconnect the media somehow through - Timeline >reels >Load from desktop - although I'm not entirely sure how I was able to do it as I can't get it to reconnect again. I've tried to link it to the source clips in the desktop viewer via "Load from Desktop" but that doesn't do the trick. I've located all of the .dpx files however these aren't seen by in the SpeedGrade Desktop.
It would be good to understand why SpeedGrade loses the files each time I reopen the project. Has anyone else experienced this or have any insight on a solution?