Matt,
Before you do anything else, just check if you have the 'yourfile'.pds.bak in the folder you saved the .pds project file.
If you have, and if PD hasn't done an auto backup of the 'trimmed' file your original backup file might be intact and you may not have lost everything.
Best thing to do is copy the .pds.bak file (so you have a backup) then rename the original .pds.bak to .pds and see if PD will open it.
One of the key principles in anything other than quick and dirty editing is to do frequent and sequential backups - 'yourfile1'.pds, 'yourfile2'.pds etc etc. It seems tedious but it really is worthwhile as it allows you 'roll back' your project to a previous position if/when a problem arises.
Once you've finished, use the pack function to 'pack' the project to a backup locaton for archive.
Cheers
Adrian
Life is really simple, but we insist on making it complicated. (see below)
Confucius
AMD Phenom IIX6 1055T, win10, 5 internal drives, 7 usb drives, struggling power supply.