It is not completly random. It is on a 12 hour respawn. I've camped it several times to prove it. If its on the same timer as Lancelot look for it between the hours of 11am CENTRAL STANDARD TIME and 1pm or 11pm and 1am. Also a hint for Snakecharmers is 9am CENTRAL STANDARD TIME, 4pm, 9pm and 4 am. I've never had it not pop at these times.