Not quite sure when we will get to this, but we probably should fix it. Currently, you can't get back to the .dat files used to build your library, unless for some reason they do not contain valid references to what BiblioSpec considers the Spectrum Source File. If the .data files contain valid pointers to your Spectrum Source Files then these are used inside the library instead of the search results file, which could be .dat, .pepXML, .mzid, etc.
It seems like we should add a column for the search results file to our source files table, as this would give a more complete picture of how the library came into existence. Obviously, the spectrum file is often just one part of the source information.
Thanks for pointing this out. I have assigned this to Matt Chambers who currently owns the BlibBuild library builder. Kaipo has left the team.