Mizzou will have to ask NC State very very nicely.
They didn't release him to Missouri because they're scheduled to play them in a non-con game.
That said, Haith and Fuller should be on a plane immediately anyway. If Purvis decides that Mizzou is home, I would imagine the bad press would be enough to convince NCSU to release him to Missouri and/or convince Missouri to cancel the game if need be.
Yeah, getting Purvis to replace NWC's scholarship while also replacing Pressey would be wonderful