Managed to recover both artifacts but feels more like worldedit rather than actually playing the game.
Workflow is,
-Locate the actual location artifact's taken to. Justice menu interrogations are helpless in this, I assume because interrogated target cannot implicate anyone else who's not a - alive and b - on the current fort. ( You will notice if a tantruming dwarf dies during / result of the tantrum, all the disorderly conducts will accuse "Somebody") Use legends maps.
-Embark on top of the cave on the map ( easier if they are set to visible during worldgen )
-Either prepare (equip&train) or just bum rush the cave with 7 wrestlers. My target was a lone goblin so biggest problem was finding him in the 2nd cave layer which his worldgen cave connected to ( Mountain enterance connects to cave level 1 , which connects to cave lvl 2, connected to 3rd and magma with a magma chute. Adamantite discovered! )
-Artifact has now disappeared, magically transported to below eerie pit level, here's where the cheating starts.
-Use L menu to find the artifacts and select them, claim them while you are at it
gui/gm-editor when artifact is selected, before you do anything else, change the temperature data ( for some reason all heat related data is 0, make them same as a non bugged artifact I used
spec_heat 420
ignite_point 10508
heatdam_point 10250
colddam_point 9900
boiling_point 60001
melting_point 60001
fixed temp 60001
(Failing in this step may end up in artifact vaporising upon messing with other tags)
Change x y z values to the same as goblin's old socks or (wherever you want really)
Set flags to
on_ground true
artifact true
artifact_mood true
temps_computed true
weight_computed true
Everything else false.
Artifact is now wherever you set X Y Z to. However, you can't properly interact with it now. ( Can't select from k menu at least. It's still visible in L list )
Build a pedestal and tell dwarves to display it there. Deconstruct the pedestal, and congratulations you have just recovered your artifact. Transport it to where you want using your favorite method ( Haul via adventurer is one way I can think of )
Considering in my case item in question is a crappy amulet and a gauntlet ( I thought it was a bracelet ), when I do this in the actual play instead of the test save, I'll embark with 7 wrestlers and as many dogs as I can. Soon as the warlord's dead, I'm abandoning the fort to ruin. It's not about the money, it's about sending a message.