Apparently Belushi's appearance wasn't appreciated by Cocker, because it was not planned, and it stole some of Cocker's fire. You can see the scorn in Cocker's face, anytime he glanced at him.
Of course he may also have been miffed because - let's face it - John Belushi did a better Joe Cocker than Cocker himself!
In any event, they have probably again performed together, except this time on "SND"
Cheers!