I had something like this happen to me during the Jester’s Festival one year. I got caught after trying to steal the apples for the Princess pig quest, and when I paid the bounty to get it over with, I saw in my chat log that the guard had confiscated an expensive purple recipe from me. It was a festival recipe that had just come out of the previous quest’s loot coffer, so it definitely wasn’t stolen.

It turned out that I had actually stored the recipe in my bank prior to starting that pig quest, and for some reason the add-ons I had running detected that I no longer had the recipe and printed that “the guard confiscated it” when he took my money. I only realized this after turning in the quest and looking in my bank, where I found the recipe (which I had only gotten one of). So check if that might be the case for you too. Otherwise, I would file a ticket - but be aware they may decline to replace your poisons because add-ons can be faulty like this.