without a picture no one can really give you any good advice as to whether it needs to be repaired.I am not able to access this area to get any pics. This piece of wood runs in the same direction as the plate but I can't imagine the roof trusses were attached to it or else the roof wouldn't be standing anymore. Maybe it was a shoddy repair that someone else had done by nailing it onto the plate? I hope that may help you in trying to identify what part I'm talking about.