I bought an item from the flee market (it was the sun apparel item) for one moonstone. when i checked for the item after it wasn't in my inventory but the one moonstone was still spent.
If I had to guess what happened, the listing was listed at 1 moonstone by mistake and the user who posted it cancelled their listing at the same time that I purchased it, causing an error where my moonstone was taken but I didn't get the item. I bought an eclipse at the same price (i still think it was probably mis-listed) and received it no problem. also I know for sure it took my moonstone still cuz I only had two at the time, so after buying the two items I had zero lol
[EDIT] okay, i feel sheepish, it was actually a mistake on my part so NO BUG. I had accidentally applied the sun apparel item right underneath the eclipse item without realizing it so i do indeed have the sun item ^^; oopsie!