Traveling Merchant

506.3.e.5. A trigger would cause a player to draw or discard. (Example card: Traveling Merchant)

509.4.b.1. A player plays Traveling Merchant to Reaver's Row. They immediately change their mind and choose to play it to their base instead, or choose not to play it at all.

703.4.c.4.a. Example: A player has two total copies of Traveling Merchant on their registered decklist, one in their Main Deck and one in their Sideboard. During game one of a match a player draws and plays one Traveling Merchant. On a later turn, they draw the second copy and realize they forgot to de-sideboard. At this point, since both Traveling Merchants have been drawn, restoring the deck is not possible as there is no easy 1 to 1 swap that can be made to restore the correct deck state.