As previously reported, former two-time WWE Champion "Psycho" Sid Vicious, f.k.a. Sycho Sid, was the only legend advertised for WWE RAW Reunion that did not appear. While no specifics were given, Sid reportedly pulled out of the show several days ago, according to Dave Meltzer on Wrestling Observer Radio.
WWE apparently knew that Sid would not be appearing before they created the graphic for the "RAW Reunion" shirt below, which was released last week. Sid was also not featured in updated promotional material before the show.
Since leaving WWE in 1997, Sid has only appeared on a pair of RAWs in 2012 as part of RAW 1000. Sid defeated Heath Slater on an episode of RAW leading up to the special, and also appeared on RAW 1000 itself as part of a segment where several legends beat up Slater.