Unfortunately because you bought your car privately you don’t have access to an ACL statutory warranty. In such cases you’re at the mercy of Holdens or the dealers good will… and they don’t have much of that these days
In any case, Holden would have records of all warranty work done to your vehicle and who did what, even if it was done prior to vehicle sale… You could request such info if you’re curious and then discuss with the dealer that did the rocker recall.
But there is little benefit in chasing this since non Holden certified dealer service have opened the engine up by taking the rocker cover and Holden or the dealers that foobared the recall will play even more hardball blaming a 3rd party mechanic (even though it looks untouched and factory rocker bearings, etc, no mods)…
The simplest thing is to buy 2x new rockers and do the trunion upgrade. Hopefully your valve guides haven‘t been excessively worn due to valve stem side load. In any case, if you don’t want the cost of taking the heads off, just do the trunion upgrade and you’d quickly find out if you still have noise or the engine uses oil. Then you can take it further by removing the heads, checking valve guide clearances and such…
Thanks for sharing such a foobared assembly (be it caused in Mexico at time of manufacture or at a Holden dealer during the recall or some 3rd party mechanic post sale)…