Quote from I am...:
Nomads might not be as dumb as you think. Next you'll probably tell us pirates occasionally forget that they buried a treasure chest. While they may occasionally forget where they buried, having lost the map, they generally do not leave such things behind unawares. The reasons for leaving a library buried in a jar in the desert may be similar to the reasons there may occasionally be buried treasure found here or there. Pirates buried treasure for safekeeping. Owners may have buried treasure to keep it safe from pirates. And through time and circumstance, no one comes back to claim the buried treasure.
The reasons for the burial of a library of related (contra orthodox) books in Nag Hammadi would most probably correspond with one of the circumstances above, most probably the last circumstance. If a caravan felt threatened, the owner of the library may have buried it. But an ambush of a caravan would not leave much opportunity to do so. Therefore, the most probable reason is that they were part of a library nearby, perhaps a monastery, which was ordered to destroy certain kinds of documents as the orthodoxy evolved.
Nomads forgetting such a library (buried) behind is not comparable to Doyle forgetting a chest of literature in his basement. It's already improbable enough that one man with forgetfulness in a house full of stuff could lose something like that...though it may be possible. It's even more improbable that one nomad, or a group of nomads, would forget and leave behind what was probably their most valuable possession besides water and camels and tents.
Evidence of textual (docrinal) persecution is the most probable of the possible reasons why a jar full of controversial books would be found buried. If there is corroborating evidence that such books were expunged in those days, then it adds to the probability that this is the reason the books found in Nag Hammadi were found buried where they would not likely be found for a while. There is evidence that book burning was practiced in those days by ecclesiastical authorities with regional jurisdictions.