In #25286755 on oregon between turns 13 and 14 my Merchant Guild just wasn't there - I had my whole deck in my hand eventually, and it was neither there nor in the trash nor of course played cards, so I bought another one. The opponent was as astonished as I was that I couldn't play the first one.
After finishing the game (next turn) both showed up in the summary.
Research is to blame:
QuoteI plays a Research.
I gets +1 Action.
I trashes an Estate.
I sets a Copper and a Merchant Guild aside.
The "I" is you, the Merchant Guild was under the Research card and thus you couldn't draw it later.
Thank you very much for clearing that up. Feeling very silly, as always in cases like this. Should I remove the post since it's not a bug?
No, let it stand. Other players may search for something similar and find this thread.