Green’s Dictionary of Slang

(Aus.) abandoned.

1958		R. Prather Scrambled Yeggs 33: When the body’s posted, he’s so full of hooch he could stay drunk for a week.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxviii 10/2: posted: To be left waiting.
1988		‘Siriusly’ Speaking in Just Us (H.M. Prison, Beechworth, Vic.) Dec. 26/2: postedv.leave [someone] abandoned [...] (he left me posted).
1993		M.B. ‘Chopper’ Read How to Shoot Friends 169: I got pulled into several crazy ploys and plans, and got left posted, resulting in blood hitting the footpath.