Thanks for reporting the problem, janigan!
I just played a game and Trading Post behaved normally.
What may have happened is that when you played Trading Post, you only had multiple copies of the same card in hand, like 3 Coppers or 2 Estates or something similar. In that case, since there is no real choice what to trash (Trading Post's trashing is not optional), the game will trash 2 cards for you (doesn't matter which, they are the same). In that case, you end up with the Silver in hand without you doing anthing and Trading Post is already over.
If that was not the case, do you remember the game number of the game, or if it was a rated game (this may help to find the game number)? It's always possible that a combination of things created a bug that can't be seen otherwise.