I made the seemingly common mistake to delete a character perhaps a month ago, it was a lvl 50 Striker that I had boosted using Knowledge Transfer. I do not remember the character’s name, though here is some of the apparently necessary information :
Region : EU West
Server : Shadespire
Class : Striker
Level : 50 (knowledge transfer)
Current main : Ragnhildr 1415 Scrapper
I just unlocked a character slot to make sure there’s enough space for him.