My wife worked for a municipal water utility which possesses very old (early 19th century) records that shed light into how certain developments in the city's history progressed. Today that equivalent information is all electronic and most will be inaccessible in a decade or less.

Getting insight into how people thought in the past will be harder for this era. Letters are replaced by electronic communication that is difficult to save and store casually. Things like annual reports are electronic only.

Lost Greek works weren't lost because they weren't recorded. They were destroyed by the fall of that civilization and the wars and chaos that followed.