Not having since this last post by you, I did the same, and came to the same conclusion.
However, it should be noted that on two occasions a Senator elected without major-party opposition retired before the next election and saw his seat go to the opposing party. In 1968, Republican George Aiken was reelected to the Senate with 99.9% of the vote (I assume that the ither 0.1% went to write-ins), but he retired instead of running for reelection in 1974 and Democrat Pat Leahy beat Republican Richard Mallary by 49.5% to 46.4% (Leahy becomng the first Democrat ever elected to the Senate from VT since the party’s founding 150 years prior).
And in 1990 Democrat David Pryor (current Senator Mark Pryor) was reelected to the Senate from AR while completely unopposed (he got 100% of the vote, so I guess they didn’t report write-ins), and when he didn’t run for reelection in 1996 the seat was picked up by Republican Tim Hutchison with 52.7% of the vote.
While I doubt that Mark Pryor will retire (maybe he would to run for the open governorship, but everyone expects retiring Congressman Mike Ross to run and clear the field on the Dem side), he might do his father one better and give his Senate seat to the GOP by losing himself. And to add to the irony, maybe Tim Hutchison’s brother, Asa, can recapture the Senate seat in which Tim H. succeeded David Pryor and that Mark Pryor later wrestled from Tim H.