I've also lost my BURG.L. Last time I remember seeing him is when he sent me to find Wendell's SCA.B, and by the time I realised he was gone, I didn't have any saves left where he was still around to revert to. I've already turned in the four super chips from the lower yard, but I have two auxiliary chips yet to deliver.
I'm on PC, single player, game version 1.05