After much deliberation, I have decided that in 2 player games, each player still only gets 2 Trinkets. I think this balances Locket (and keeps with its intention of discouraging trashing), and all the "variety" based cards. Forager is the biggest concern, but I think that it will be balanced and interesting, even as it's game warpingly dominant, as each player has a unique opportunity to add to the value of the foragers with their own trinkets.
Bell was the hardest decision of all the trinkets, so I'm not surprised it's one of the most criticised. I didn't want any of the trinkets to be "worse" than copper, and there's more terminal drawers than "draw up to X" cards, so +1 action would be worse more often than not. +2 actions will give a big advantage on some boards, but not on others, and the way it interacts with terminal draw cards is interesting (and probably neutral). It will be an immense advantage in cantrip+terminal boards with no other villages, but it might not be the best strategy on the board for the other players with their trinkets.
Dagger's purpose is the self trashing, but I didn't want that to be triggerable in every game, so I gave it the moat thing. The blocking's a good way of making it count more in games with trashing.
I might make Key to the City "+$2 for each empty pile", but it's meant to just be a nice little bonus for holding onto the Copper.
One thing I like about "Locket" is that there may be some strategy in keeping it hidden (now that you only get 2 trinkets) to trick the other player into ending the game on a loss. You could even hide one of the other trinkets to bluff it.