If you perform magic, each of those three options should look fair. But if you position yourself like a cardman, none of those are applicable. But that's just my opinion.
By this logic, it would be just as fair to an audience were the magician to hand them a card rather than letting them choose one themselves. After all, if it's magic, it's magic, right?
An audience never
assumes you are doing magic. In order for them to experience magic, you must ensure that they can conceive of no reasonable explanation to something you did, and in the case of finding a selection, the less than can be known about the location of he selection prior to finding it, the stronger the magic.
Also, if you assume the actions ARE completely fair in each of the cases I have presented, in which case would the card be harder to find?
In the first instance, even with no breaks or anything, you no roughly where the card is in the deck. The audience knows roughly where the card is in the deck. In the second case, while it is not possible to know where in the deck the card is, it is clear that the cards have not been mixed much, so the cards the selection was placed with are still with the selection. In the final case, there is no knowing where the card is or what cards it is with. These are things which an audience can still understand even without making a concious effort to do so.
Of course, in some rare cases, it might be better for the audience to believe that a card is in the middle of the deck, for example, during an ACR; however, this is quite different to a card being lost, which is preferable in most routines.
Joe