Can Rickon search a second card in the hold, or since it is considered out of play and therefore not your deck you cannot ?

Same question with galbart glover (search in the discard pile).

Both cards specify "search your deck" and the Hold is not part of your deck, neither card gives access to the Hold.

elwe said:

Not only do both cards specify "… search your deck…," but, even if they didn't, neither effect currently in the pool allowing you to get cards out of the Hold (Black Sails, and Naval Reiforcements plot) are search effects (agenda is choose and add to hand, and plot is reveal and add to hand).

So, no, neither would work to that effect.

Note that the cards in your deck are out of play (like cards in your hand, discard pile, dead pile, shadows and hold). The main point is that your hold is not your deck, however.