USA 129 itself (I believe) produced a flare of mag. 0 low in the east at about 20:11:00 and remained bright for tens of seconds after that. I catched it still being +1 some 20 seconds later.
More later, including (I hope) the flarer ID after I have measured the image and have dan an ID run with the positions.
Update: the flaring object is identified as Metop-A, 06-044A. With thanks to Russell Eberst and Arnold Barmettler.