User blog comment:Ohatsu/recovering data/@comment-23878607-20141017141212

If the old pawn is hired by someone else and kept in their game until after the new pawn is uploaded in the Rift the first time, then you can keep the pawn's accumulated knowledge. When the old version returns, its knowledge is merged with the new one.

Otherwise... I am sorry to say, everything else is lost. It is always advisable to back up a single save file to an external USB drive for just this reason.