Here’s a link to the USGS showing an earthquake in that area in the last 7 days.
http://earthquake.usgs.gov/earthquakes/recenteqsus/
I looked on the internet and couldn’t find anything else on it. I don’t doubt your word but do find it odd that there’s no mention of it to speak of.
Both your links show that earthquake.
I did find it curious that there was no mention of it on Drudge.
The source of the seismicity isn't necessarily magmatic in origin -- not necessarily due to movement of magma. It may be due to plate movement. The seismologists' determination of the epicenter's depth will tell you -- the Nazca plate is present at depth, but the depth is very great in Wyoming, near the leading edge of the plunging overridden plate, much deeper than the Yellowstone magma chamber. (National Geographic had a good article on the Yellowstone hot spot recently.)
The hot spot, of course, is connected by a magma feeder to the magma chamber; this feeder penetrates both plates and has emplaced the magma body in the North American plate.
One temblor probably does not signal a problem. Swarming low-intensity quakes would be another matter.