Im leaning towards Welsh/Welsh mix. It doesn't look exactly like a Muscovy to me IMO. What are you feeding it? Make sure that what ever it is, its NOT medicated
EDIT: Its wings are small because of its age, but as it gets older they'll get bigger. Plus the feathers are what make the birds wings look so big, not the actual meat of the wing
If you have the space to keep it and you want to, I suggest sexing it and buying another member of the same sex to keep it company. If you don't want it then I suggest talking to your local shelter, or if you have time to wait, post it in the auction part of this site (I think that's the correct place, you may want to look at the rules of the board before posting). If the shelter or a vet can't help you, I'm sure they can put you into contact with people who can. If they suggest just letting it go, then they're wrong. It's too young to be on it's own. Good luck!! You're a good person for picking it up! If you decide to keep it then I hope you have as much fun with her as I do mine!