My Muscovy has been on our 1/2 acre pond for a day and half. I've tried scaring her off and back to the orchard pond. Now I'm trying a live trap. She walks all around it, but has not gone in.
Can she see / hear your other ducks from where she is? I once had a hen go off away from the fenced chicken run. I tried everything I could think of to get her back through the gate (the other hens were already in the barn when I discovered she was missing). Finally I let a couple of the hens back out in the fence and she went running right over to be near them.
That's the best I've got!
It took almost 4 days, but she finally trapped herself. Brought her back to the orchard. When I let her out, the male and the other female greeted her with song and dance. Then the male nailed her, kind of rough, you'd think she would have drown. I see babies in the future. :~)