The Scottish women lost an extra-end final 5-6 to Russia in Karlstad, a game in which their previously excellent form deserted them.
Amid errors by the whole team, Muirhead missed a take-out in the fifth end as she tried to blank, giving Russia a 3-2 half-time lead. She was short with a draw in the ninth for the third of the Russians' three vital steals.
The Scots, having set up the extra end well with two early centre guards, saw Russian second player Margarita Fomina produce the shot of the game to clear them both and take out a Scottish counter on the four-foot ring. Russian skip Anna Sidorova then hit and stayed for the one shot needed to claim the title.
Muirhead said: "We've played better this week. We just missed one or two slack shots here and there, and they played well. [But] we've got to take a lot of positives from this tournament. If at the start of the week, you'd said we'd get to the final, we'd have taken it, but when you get to the final you don't want anything but gold. And, having come away with the gold last year, it makes this silver tough."
The men, led by two-time world silver medallist Tom Brewster, suffered illness and poor form as they departed from the tournament early, ranked seventh, despite twice world champion David Murdoch being introduced to the line-up.
"We've not had a great season for various reasons. A lot of people are going to say it's because we brought Dave into the team, but that's got nothing to do with it," said Brewster. "We're just not making enough shots. We've changed techniques, our style of play, and altered quite a few things. We're still getting to grips with that. That takes time."