Thanks for the report!
While a screenshot is nice, giving the actual game number is also immensely helpful, because it allows to examine the exact circumstances. There could have been cost reduction or something similar, for example, to make Silver unisuitable to be gained. Luckily from the screenshot I could find the game and look at what happened.
When you bought Farmland, two different things triggered:
1) Farmland's ability to trash a card, gain one at cost +$2 of the trashed card.
2) Hovel's ability to simply trash itself, because you bought a Victory card.
On my replay, that got me two buttons to choose from: One with Farmland (option 1) and one with Hovel (option 2).
Now, when I pressed the Farmland button, I did get to choose between the $3 cards (Silver, Market Square, Watchtower) for gaining.
OTOH, whenn I pressed the Hovel button, Hovel was trashed and since Hovel was the only card left in your hand, Farmland's ability had nothing to trash, so nothing to gain.
My assumption is that you clicked the Hovel button. My log in this case looked exatly like your screenshot.