The pekin you are seeing is likely not the same one. The one your friend set free is likely dead and all you are seeing is another one dumped cruelly.
Domestic ducks "set free" like you propose have an average lifespan of SIX
months. If they are not killed by park visitors and their dogs, they are prime targets for raccoons, coyotes, eagles and the like. They get killed by overmating from the other drakes and ganders who kill off all the females by gang rape. The low males in the pecking order end up being the "females" and end up overmated, too. They have no instinct to forage for their feed and end up dependent on handouts from people. Usually those handouts are bread. Bread has NO nutritional value. The ducks end up starving.
http://www.duckrescuenetwork.org/duck_care.html#never
If you are going to release a duckling, you may as well just euthanize it and bypass the suffering it will be subject to.
Domestics are dependent on their keepers for food and shelter and protection.
In Oregon it is a class three misdemeanor to dump a domestic animal in a public place. And I do everything in my power to see the authorities are alerted to such dumping.
I can't tell you how many ducks I have rescued from our local park suffering from wounds from overmating, suffering from deformed and diseased bones from malnutrition. I get people who bring me a "sweet little duckling" they got for Easter who can't walk. It was fed bread and birdseed. If people can't commit to an animal they have no business having it in the first place. It is heartbreaking, frustrating and maddening.
We had people beat a muscovy drake to death because he was funny looking.
Recently a couple of teenage boys ripped the intestines out of a setting hen, destroyed her eggs and beheaded her. For fun.
http://www.localnewsdaily.com/news/story.php?story_id=120494601464703100
This is what dumped ducks and geese look forward to and if they escape such cruelty, they are lucky.
I would suggest that you contact someone on the Duck Rescue Network website and find a home for that poor animal.
I am on the board of directors for the Duck Rescue Network and I guarantee you we will do everything possible to help you find a home for your duck.
Please don't dump it.