I doubt an obscure stream will do it. Extremely few of the freestone streams ...
Who said anything about freestone stream
I am thinking more along the lines of pond escape to a fertile stream that has a refuge spring, very non-traditional trout water.
I guess anything is possible if you stretch the odds long enough. That seems wildly improbable though. You'd have to have a trout with the genetics to become a record,
AND that trout would have to be in a pond,
AND the pond would have to be near a fertile stream,
AND the stream would have to have a spring that ran cold enough to keep the water under 70 degrees year round,
AND the spring would have to be in a pool big enough and deep enough to house a predatory fish in the neighborhood of 30 pounds,
AND someone would have to find that fish there and catch it.
I might run into Britney Spears on my lunch hour and she might invite me back to her hotel for some alone time, but it's probably not a likely thing to bet on.

With the SoHo's population of browns, large forage base, and track record of producing big brown trout, I'd say it's got to be the odds-on favorite.
bd