DeYarmond Edison (aka Justin Vernon‘s Old Band) at The FADER Fort at SXSW (03/19/11) Photo: D. Caplan By 7 o’clock on SXSW Saturday rumors were swirling about an unbilled “special guest” appearance at The FADER Fort, thinking I was “in the know” I told everyone it was going to be Bon Iver appearing under the…