Trashing a Fortress in supply with Lurker is something commonly done. That way you put it in your hand but haven't gained it.
Thanks to you guys for the examples. Most were not surprising to me, but Fortress-via-Lurker does surprise me. I get it, intuitively, for Masquerade. That's clearly some sort of exchange. But not true for the via-Lurker example. I guess you gain it but do not "gain" it.
I guess it would be more accurately stated, "You get it, but do not gain it." ...and this just has to be taken on faith.
By the way; given the above, it's weird that cards obtains via Mine are 'gained.' You get rid of one card and get a different card (or even the same card, of course, if you want and it's available). The text of Mine make it clear that it is "gained." But the logic of getting rid of one card and getting another one seems *really* similar in real-life effect to Travelers...even if the text on the card is different.
But I can see why (1) No one wants 3 paragraphs of exquisitely-crafted detailed instructions--which would require a magnifying glass to read!--for kingdom cards.
, and (2) how language on a card that was perfectly clear in a kingdom could, later, become ambiguous or opaque down-the-road, due to some new wrinkle in Dominion--like Events, or a Possession-type card, etc.. It's part of the fun for me with this game. As a lawyer, I really enjoy exploring edge cases. Not sure if that is a feature or a bug with my personality.