I believe that I read on another post that the ref was questioned by one of the Irmo players about this, and his response was that he did not see Gus (or Goose) take OFF his jersey, he only saw him putting it back ON. (huh?)
Now, personally, I think that answer is a little silly. Sure, I understand that the ref did not specifically see the keeper doing that, so he couldn't give him a yellow card for it, but he had to "KNOW" that is what he did. That's what the ARs are for. So, he could have given the keeper a yellow card based on the ARs observation.
And, I am not blaming anyone for anything here...merely answering the lady's question (okay, and adding just a tad of opinion).