I definitely understand that only one person gets each card from the Secret Market or Black Market deck. My concern was more that you could get a Bureaucrat and a Possession for the same effort. With Black Market, you actually have to pay up, so there is a cost to managing to get something like Possession. Black Market also gives you a choice of cards as well so you're not sad if the top one wasn't what you wanted.
Gaining the card instead of buying it is definitely better rules-wise, and helps make Secret Market different from Black Market, so I would try to find a way to keep that approach. Maybe let you pick between a couple cards with gaining one optional? You could also change the +$2 to something like, "If the gained card costs $3P or less, +$2", for balance, but I'm disinclined to make it wordier.
Gaining a copper get out of jail free card.
It's definitely good to have the alternative, so there's not mandatory multi-card trashing. Maybe I meant amusing, more than odd; I wasn't implying you should change it.
Plus if you want to make it an easier guess keep your coppers, you’ll guess right almost every time.
Keeping your Coppers might help you get to Secret Market more easily, but there is the opportunity cost of, what if I ignored Secret Market and did something else instead?