hi james
by the distance that would be normal. If the master took a more southern route, than he will stay away from South Afrika. I assume you look for AIS, if he stays only 100 plus nm away from there, then he does not pop up. Next you should possible see her again when transiting the Malakka Strait. Aso, some Masters also switching AIS off,,which sometimes if not a bad thing anyhow
brgds
capt ted