SDG-6 has been recovered! This morning I spoke with the gentleman who found the balloon - Mr. Ryan Bryant, a Realtor from Cumberland County, Kentucky.
Mr. Bryant said that he saw the balloon caught on a powerline along Highway 61 North in Cumberland County last night at around 7:30pm Central Time. This was a very fortunate event, since the area is otherwise quite remote.
After he cut the payload line, Mr. Bryant said that the balloon envelope took off into the sky - so its flight wasn't yet over! (Having been relieved of the payload, the envelope would have developed a very high superpressure at altitude and most likely burst within 10-15 minutes of leaving the powerline, so it's probably not too far away.)
The payload is now safe and will be on its way back to Michigan sometime soon... Our thanks go out to Mr. Bryant for a wonderful end to a wonderful flight!