No, because pinch hoppers description says: "when this card you control is send to the graveyard", that means you must have pinch hopper on the field. Face up or set.
There are some really nasty OTKs that are made possible with Merchant. I've been testing a deck that runs 3 Lycanthrope and 2 of its ritual spell, 3 Merchant, and the rest of the deck is vannilas. You can usually end up dealing upwards of 4000 on turn 2-3 with a good hand if you use Kaiba's Beatdown skill.