The 22-year-old lost just one game during the round-robin stage in Latvia, that 11-2 to Swedish skip Sigfridsson on her second outing, with the two nations locked at the top with ten wins from 11.
That guaranteed that Muirhead and Sigfridsson would play for a medal in the latter stages and first they faced each other in the page one-two play-off with the winner automatically qualifying for the final.
After blanking the first end, Sweden hit to score two points in the second before they swapped singles all the way to the seventh with Scotland taking the lead for the first time in the eighth.
They stole for two and a 5-4 lead however Sweden scored three in the tenth end for a 7-5 win and safe passage into Sunday's gold medal match while Muirhead and her Scottish rink go into the semi-finals.
There they will face either Canada or USA, the latter emerging as the winner of the tiebreakers with a 7-4 defeat of Switzerland who earlier ended European champions Russia hopes with a 7-6 victory.
Canada and USA meet in the page three-four play-off with Muirhead, a world silver medallist from 2010, certain she can get the better of Sigfridsson if they are to face again for gold in Latvia.
"That totally got away from us. We had a hellish pick-up on my second-last stone in the last. We had that end sealed up but that's curling. You get these unfortunate breaks and what can you do?" said Muirhead.
"We had to be patient out there. We knew that we could play the shots and we knew that we were playing well. Our chance came in the eighth end. If my second-last stone there hadn't happened, we had that sealed up.
"We knew we had to play well against them if were to have any chance to win, but I feel like we've been robbed a little bit. We've got to come back now in the semi-final and put in another good performance.
"They [Sweden] are a beatable team. Yes, they played strong in the round-robin, but when it comes to play-offs they're definitely a different team."