In the log below, when I bought a Farmland, it forced me to trash the Province. It didn't give me a choice. I should have been able to trash any card but instead it looks like it forced me to trash the only Victory card I had in my hand.
I would have rather have trashed one of the Coppers and then gained an Estate. Because of this bug, the overall Victory points change was -6 instead +1.
Turn 17 - julesreid
j plays 4 Fool's Golds and a Silver.
j buys and gains a Duchy.
j draws 2 Coppers, a Province and 2 Fool's Golds.
Turn 17 - Lord Rattington
L plays a Laboratory.
L draws 2 cards.
L plays 2 Coppers.
L buys and gains an Estate.
L draws 5 cards.
Turn 18 - julesreid
j plays 2 Fool's Golds and 2 Coppers.
j buys a Farmland.
j trashes a Province.
j gains a Farmland.
j shuffles their deck.
j draws a Copper, an Estate, a Duchy, a Province and a Fool's Gold.
It seems that you played your coppers and the province was the only card inyour hand (and thus trashed).
If you want to trash a Copper, don't play it before (so don't use the autoplay treasures button, which plays ALL treasures)
Aha. Yes, I probably clicked on autoplay. Thanks for the clarification!