Generally I think that unrecorded deeds are a canard some researchers use to spare themselves the agony that the records they need really no longer exist. A lawyer would say it was introducing facts not in evidence. However, unrecorded deeds did happen. The purpose of recording the deed was to make a public record of land ownership. However, as long as you had an actual deed to show someone, that was legally sufficient. If the deed got destroyed you were SOL.
However, you can see in the sketch of Samuel4 (William3) Wallis that there must have been an unrecorded deed, because we have the two deeds on either side of the missing one. On 17 December 1754 Thomas Bickford of Epsom, husbandman sold to Samuel Wallis of Barrington, husbandman, 60 acres in Epsom, it being lot #89 in the third range and 32 1/2 acres in lot 88. [Rockingham Co. Deeds 61:145] Then his son Nathaniel forty years later on 27 August 1792, as Nathaniel Wallis of Epsom, yeoman sold to Joseph March of Deerfield, a certain tract in Epsom, lot no. 88 in the third range and a lot containing 32 1/2 acres "land I purchased of my honored Father and the farm that I now live on." [Rockingham Co. Deeds 135:77]. The description of the land is exact. However, the intervening deed from Samuel to Nathaniel was never recorded.