Do you live near water? farms? Busy roads? I'd notify neighbors to let you know if they see her! This is an out there suggestion buuuuut, my ducks come running to each others sounds (typically the male "come here" sound and the girl "oooo I found something good to eat" squeals), so you could try either keeping some (who won't fly away) near where she left hoping she'll hear the sounds, or you grab a speaker--and hear me out--hook your phone up to it and play muscovy call sounds, either from YouTube or ones that you recorded yourself. You could try that, putting it near the place she took off for the day and hopefully she'll hear it and come home.
Other than that, you could let your local police/fire department know you're on the lookout for a duck as she might turn up somewhere funny in town!
I hope she comes back!!!