There are a few possibile explanations for the lost edits that I've seen on the forums from people including: 1) bad geometry, 2) layer locked by another instance of ArcGIS, 3) corrupted project or template, 4) accidentally saving the project not the edits, etc. You might Google on something like ArcGIS edits not saved. Sometimes the edits are there but the symbology or definition query doesn't show them; bringing them into a new project might show them. Another possibility is that they weren't saved to the hard/network drive, which might only happen for sure if you closed editing. Something similar might be happening if you tried to export your shapefile or the attribute table, it could go out without the "saved" edits. I don't know where they are stored, perhaps in a cache or stack somewhere. I've often lost the last few edits while others that had been saved were in fact saved. So I try to remember to close editing every so often. I know of no way to recover truly lost edits.
