Yep, he did. Buck's signature is in black, Stringfellow bottom left and Mills bottom right.
The physical condition of the setlist isn't so good - it was perfect when it was given to me by a stadium employee (the Reitstadion Riem, a 1972 Olympic facility), and when Mills and Stringfellow signed it that night. But the concert was in Munich and I had to catch a train back to Stuttgart, where I lived, later that night, and the skies opened up in a downpour as I walked to the bus stop to get to the train station. So the paper got drenched, and ultimately wrinkled. It's still a treasure to me though. Mills and Stringfellow were both very chatty, and seemed happy to talk to another American. Stringfellow liked that my name is with a "K" rather than a "C", and talked Norse mythology with me for a bit (hence the "Ragnarok" comment). I didn't know that he wasn't such a good person at the time, but he was cool then.
Peter Buck also signed my Drink the Sea concert setlist at the show in February, along with fellow band members Barrett Martin, Alain Johannes, and Lisette Garcia. The only REM cover that night was at the end of the set, The One I Love.