At one time there were fires in document storage facilities but with everything being digitized, backed up and archived, things become more complicated. There are still ways to destroy evidence but people like Pelosi don't know how to do anything themselves and those people who know how know better. The Pelosi's of this world depend on classification, security concerns, privacy laws, donation to libraries, multi year future release dates and a multitude of other schemes to hide things. [Remember the search terms "Comey" and "Coney"] If the right people want things to be found, they will be found.