This^. Terry destroyed the mask with the recasting process. I think people just used “stole” to describe what Terry did because he “took it and didn’t give it back”, but as Rod said that is because he destroyed it. His original intent isn’t confirmed (to my knowledge) but I imagine he planned on using the recast to produce more masks and to return the OG Kirk to Terry. The bad recast was just his attempt at covering it up I think.
I have a saved photo somewhere of the destroyed mask but I’ll have to look for it.
In the meantime, here’s a thread from that time that I suggest looking at in addition to some of the related threads below.