I’d bury it like a tree in the ground and just water it regularly. Mid summer though....I don’t know enough, or anything really, about New Zealand weather. You might just leave it planted as is and care for it as you would usually do. It’s possible it could come back...but don’t give up to soon....it might even be next season when you see growth. I’d keep it semi sun, out of the mid day sun (if New Zealand has a hot spot in the day). I think to much sun now will further dry things. It can use some humidity....with what I’d call dappled sunlight. If it does not come back...well...you will know that you at least tried. That’s worth something.
I’ve taken sad looking trees and at a minimum totally shielded the roots...the entire grow box really....using broken clay pot pieces. Kept the roots cooler, moist but not wet. Periodically in the early morning hours I’d uncover it all and thoroughly water with lots of draining water....sort of like the morning car wash. In evenings, when my temps were hot and dry I would apply a soaking mist to the trunk. Eventually...I saw buds. And growth. Maybe just lucky I suppose.
I don’t know much about New Zealand...but I’ve always thought of it as a beautiful country. A country to be proud of always.
