Hi soulman, I recon it would have been weather avoidance. You said you lost him in the clouds. We quite often tend to avoid cloud at high levels if we can as it can be a bit turbulent.
I'd say he was a ADL MEL flight who had diverted right of track, and then maybe paralleled track then when he was clear of most of the weather he was recleared direct to a position called chapi, which is north of Melbourne for a star called the Arbey 1 arrival.
Hope this helps, and next time I divert, I'll look down and wonder if I'll make it on pprune
Conny