This is the first I've heard of this, but I may swing by that area some time this week to check it out.
I tend to agree with Mike that something like this (getting this little coverage) is unlikely to affect the ecosystem much. Several years ago, I was fishing Mill Creek in Ligonier and noticed a similar sheen, and could clearly smell some sort of fuel.
I reported it to the DEP and after they investigated they got back to me to tell me that it was oil used for home heating that had spilled from somewhere upstream...and that typically, spills of that magnitude had no observable effects on stream ecology (but that if I noticed any impact, or could still see/smell oil even 3 days from then, to get back in touch with them).
If a waterway as small as Mill Creek could handle that with no problems, I'm guessing that even a much more significant spill won't have a lasting effect on the Loyalhanna down there.
That being said, though, I don't think it's something that should be ignored or accepted as normal.