Try to open it with a compression program like 7zip. egp files are zipped archives of xml files, so you might find something usable in there.
Hint: Avoid storing egp files in a remote location (network share, workspace server) while you are working on them. EG has a habit of trashing the files if the connection is unstable. Copying egp files to a place where there's backup is OK once you're finished.
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