I understand whats going on: you lost your original .map file.
TBH: its prolly not worth trying to rebuild your old map from a decompiled version - you'll lose texturing, and will add WAY more brushes then your map originally had, because the decompile process splits the faces up into brushes much differently then you used them. This could affect the performance of your map, unless you spend the time to go thru and fix them all.
Thanks for the offer tho.
Cheers!