I caught about a six inch brookie at the 772 bridge. It was bright orange on the belly and I don't see how it could have been anything but wild. based on the size and coloration. My buddy picked up a gorgeous 17" brookie in the FFO section in the same time frame. Both fish pre-dated my owning a digital camera, so they would have had to been caught 2003 or earlier.
Regarding brookie movement, my experience has been they can move great distances. On one small trib to a larger ANF stream, I could have sworn they dumped a couple of buckets of brookies into the trib, but I'm pretty sure they all moved up from the big hole they dumped the fish in, anywhere from a 0.25 to 1 mile upstream. Their upstream progress was impeded by a set of waterfalls, but the larger holes in the small stream all held brook trout. In the same larger stream, before there was easier access to stock, I'm pretty confident that no stocking occurred except at the few limited road access points. The brookies would migrate en masse to log jams and it was not uncommon to catch 30 fish out of said log jams. The jams were often up to a mile away from the nearest stocking access point.
Probability would put your brookie as being a stocker from the derby that migrated, but I also believe there is some extremely limited ST reproduction in Donegal, so I wouldn't rule that out as a possibility.
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