Yes, Spring Creek has a wild rainbow population. There are a few throughout no doubt, but there is a particular area where they are most common, as PSUFishMenace says, and they are indeed spring spawners.
That said, there are also a much larger number of rainbows with hatchery origins, and they are concentrated around the two hatcheries (though some disperse), as well as bigger ones downstream from Bellefonte (thanks to the demonstration area in town). They escape at various stages in their lives, some of them very young, and live in the stream for years. Color is a function of diet, and fins do grow back. Thus, fin wear and color would only be reliable indicators on fresh, adult escapees, i.e. not the norm. If you catch one that looks like a stockie, it's a stockie for sure. If you catch one that looks wild, I'd still guess there's a 70% chance or more that its from a hatchery, but I don't think there's any way to tell for sure short of sending scale samples to a biologist. So, that being said, who cares? I have as much pride in a fingerling stocked fish as a wild one, it's still acting wild. I don't then see much difference between a fingerling stocked fish and a fingerling escaped fish.
If there's anything that leads me one way or the other, its number of spots. The ones I felt sure were wild, from the area where wilds are most common, were silverish with few spots, like PSU's picture. The darker fish with lots of spots, like the OP's, I think are hatchery products. But again, there's no way to know for sure, and who knows, maybe the modern hatchery products successfully breed now and then, and thus there could be 2 distinct genetic strains in the stream?
