What you said is completely incorrect. Check this out:
http://www.freerepublic.com/focus/backroom/2430289/posts?page=1
No, it's not. The "election" isn't over because the votes haven't been counted - the counties had 10 days to continue to receive and count absentee ballots.
Moreover, one needs look no further than the Robert Krueger v. Kay Bailey Hutchison special election to take Lloyd Bentsen's seat in 1993. That election was "held" on June 5, 1993, but Senate records clearly indicate that Kreuger - who was the Dem appointee temporarily holding the seat - stayed in officce until nine days later on June 14. In fact, Kreuger voted on June 10, without objections.
I've read some of the stories based on the CRS report. They're unconvincing because they all allude to language in the report that says the interim office holder's term expires immediately upon the election being held. It's difficult, and without judicial precedent, to say you've held an election, and you haven't counted all the votes.
Even with the precedent found in Powell v. McCormack case, no court would hear this until such a time that the election process was completed.