[whpalmer4]

Double-click on the backup file in the Finder. OmniFocus will open it in another window, and you can drag and drop stuff from the backup into the live database, if you wish.

Are you sure the missing actions haven't been completed and thus hidden from default view? I would take a look in the All Items perspective. It has been quite a long time since I have seen OmniFocus lose data during a sync, excepting user error.