Well, I've been playing it so we immediately reshuffle a discarded item back into the deck. I think the FAQ asked us to do that for vanilla on pg 6, so I did it for RtL as well...
That is for vanilla, which is leagues different from the advanced campaign.
RtL pg 22
Treasure and shop items are bought and sold at the Market.
Visit, Train, or Restock
When the first hero visits a given Market in a given game week, a number of cards equal to the city’s Market rating are
drawn from the treasure deck that corresponds to the current campaign level. “Treasure Cache” cards are discarded (and are not replaced, instead representing a market shortage that week).
All heroes who visit that Market that week may purchase items from among the drawn cards. Of course, once particular cards are purchased, they are not available to heroes who visit the
Market later the same week. Copper items cost 250 coins to purchase, Silver items cost 500 coins, and Gold items cost 750
coins. Any shop item can also be purchased at the Market for its listed cost; these are not drawn as above, but are always available. A hero must be able to carry a given item in order to
Items can also be sold at the Market, for half their purchase price. Sold items are re-shuffled into the decks they came from.
At the end of a given week, any treasure items that were not purchased from the Market are re-shuffled into the decks they came from.
The market is didn't than in vanilla. Items don't get shuffled beck in until the end of the game week.
FAQ pg 20
Q: Are items destroyed by Crushing Blow placed in the
A: No. Those items are discarded, and the next time the treasure deck is shuffled they will be shuffled back into the deck.
Only time you reshuffle your treasure deck is at the end of a game week. Destroyed items are discarded.