Despite being about as old as P99 is, the wiki does not have 100% of all game content in it. The Warrens in particular was only added relatively late in P99's history (the server didn't even have Velious for a long time), so it's very likely that a kobold brawler was missed.
However, it's super easy for anyone who wants to add him to the wiki. Just edit an existing mob (probably easiest to start with another kobold in the Warrens), copy it's code, go to
https://wiki.project1999.com/a_kobold_brawler and click edit, paste the code, and then change any bits that are different for the brawler.