Norton is able to pick up a deleted file fairly easily, but in this case the requirement is to pick up a deleted (edited) part of a file. When the "edit" is removed from the file, it's essentially a lost space on the drive, and the only way I know of to get it back is to read clusters by physical address and attempt to reconstruct. Because the original file was in a database format, it's not even possible to assume that the missing stuff starts on a cluster boundary, or that it doesn't span more than one cluster.
Norton does NOT make that easy to do in any of the common utilities I've seen recently. Norton may have a full-blown disk analyser, but I haven't seen it for sale in my area.
Norton works miracles, but not this particular one so far as I know.
(I'm willing to reconsider if someone can offer additional detail about how they've done it to recover a deleted fragment of a database file.)