I took a quick look at the group mentioned above (JiveWorld17 Speakers) however am not seeing where an invite has been sent to your account:
That being said, I do see where Libby Taylor is listed as a manager of that group so might be able to assist with sending out an invite to your account.
Stan was listed a "invited" by his email address, his name is not visible to the community, so that search wouldn't work for you.
That said, I've deleted the invitation and force added his name as a member. Stan, you should have access to that group now.