Saunders is a character mentioned in the story A Call to ARMS, a Lores and Histories entry found on the official RuneScape website. He cannot be found in-game, and the time in which the story takes place could mean that he is now deceased.
According to the story, Saunders was the leader of a construction crew in the Year 138 of the Fifth Age. The crew was hired by Lord Marshal Brogan to help build the Mobilising Armies camp west of Oo'glog. On the 13th of Raktuber in 138, shortly after the completion of the camp's recruitment room, a group of rogue elves entered the camp and attempted to rob it of its supplies. As part of the incursion, the elves used some type of crystal sphere, which broke open and released an illusion that took the shape of a dragon.
Saunders evidently fled the camp when the illusion was first released. Brogan comments in the story that he didn't blame Saunders, and so he presumably returned to finish the project.