I dont know what is going in your blueprints, but if you need to know when “Pawn” is out of sight, you need a track on him, so when AISense react that something is in, you mark Pawn to variable in blackboard and set bool on true, when is outside of sight of AISense then you setting bool on false.
You can simplify this process to dropping bool out, and just keep pointer to Pawn/Actor in blackboard and check if is valid ← that is your indicator if Pawn is in AISense sight