Unless you have created a backup file, or have a backup RDF file created from Clippings 5.5, your only other option is to see if your system has kept an older version of the database file, which is located in your Firefox profile folder under the folder path storage/default/moz-extension+++<
series of letters and numbers>/idb. Under the "idb" subfolder, there would a file with a .sqlite extension whose name may vary, but would look something like "220207427asegCnliipp". Windows has a feature that can keep previous versions of some files on your system; ask your IT friend if that is the case with the .sqlite file.
Alex
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AE Creations website
http://aecreations.sourceforge.net/the AE Creations blog
http://aecreations.blogspot.com/