European champion Muirhead beat China in an extra end but was narrowly edged out 3-2 by Sweden in a defensive game.
The defeat means that Muirhead's rink have now lost five of their nine matches.
It's still mathematically possible for Scotland to get themselves into the play-offs but it's also highly unlikely.
Scotland now need to beat hosts Canada, who top the current standings with Sweden and Korea, and Italy in their concluding games, while hoping other results also go their way.
"We're playing for ranking now," said Muirhead, who admits she has struggled with her form all week, despite arriving with such high hopes.