I'm not really sure where this popular perception that the Romans kept lots of records so we should know everything about them comes from. It makes no sense. Roman imperial administration was very diligent when it came to certain kinds of record keeping, particularly the various forms of acta, both private and public. But most acta were not published. The various court acta, recording edicts and so forth, were available to those in the imperial administration (notably Suetonius and the jurists used them) but were not generally published. There were various publicly-posted acta, which were published as publicly-posted tablets that survive poorly--i.e. not at all. We can only guess their contents and style through references to them and Petronius' satirical parody of their general form in part of the Satyricon. By contrast, we know of Pilate and other magistrates through epigraphic sources, which survive much more easily but rarely talk about random dudes that were crucified. The Roman world, particularly in the Principate, knew of archival buildings, but their contents are pretty much totally lost. Such things were not published, and unlike the vast majority of complete texts that we have they were not copied over and over again through the Middle Ages to ensure their preservation. We have a handful of complete or nearly-complete texts salvaged from archival buildings, particularly military ones--the Vindolanda Tablets are from one such collection--but these finds are rare and usually very fragmentary. They're a nice surprise, but to expect that we have such texts from any given year and place dealing with any given event is totally unrealistic, that's not the way textual preservation works