Shibui
Imperial Masterpiece
Chop below the container then you should be able to ease the plastic container off the chopped trunk and new root mass by pulling downwards. I assume there is a split in the container or else how did you get it round the trunk? Open the split a bit to help get it off.Now the question is how the heck do I separate it so I can just pot it up.
Usually much easier to get the container off the chopped trunk than it was to get it on an intact trunk.