The charms do work, even if they are not shown on your screen. In the description it is pointed that a charm just increases your odds of finding items, but this does not mean that you will find an item every time you explore the room. Sometimes a room will not have items in it and it is random with the placement of these items so you may have to search a room many times before you run across them. Also the charms do not affect the chances of finding a quest item.
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