Honestly...the only way THIS could have happened was if you just didn't care to actually "click" to apply for world transfer for your "defaulted merged server"...
Otherwise you would have been on it and stayed there. If you didn't select your defaulted server for merge(you have to click it anyway, it's not being selected for you), then they prolly assumed you are not among the "people who want to stay there".
Before I'd blame any mistake or misbehaviour on SE here, I'm rather willing to believe that was on your end.