Mark,
I wasn't there, but it looks like Mani, acting as a Supervisor, was trying to reach your pilot without response. So he probably tried multiple methods to get a hold of your pilot. Your pilot has a responsibility to be monitoring his connection, including attempts to contact your pilot by ATC or Supervisors. Not sure if your pilot was using a pilot client, or observing using VRC or another ATC client. If he was not observing using VRC or another ATC client, it's possible that Mani accidentally used an alias meant for someone using VRC. He will likely see this thread soon, and/or I can have a quick chat with him. However, even if it were Mani's mistake requesting a reply via VRC, the main point is that it looks, at least on the surface, like a VATSIM Supervisor needed to contact your pilot and your pilot either refused to respond, was not monitoring his connection and did not respond to a VATSIM Supervisor, or didn't know how to respond. If he didn't know how to respond, he does need to read the section in his client's documentation on how to use private messages (PMs).
Unless your pilot has a history of unattended connections, there is really no harm done here, and I would simply advise your pilot to be more mindful about monitoring his connection, ensuring he contacts ATC right away if in controlled airspace, and ensuring he responds to requests for contact by ATC and/or VATSIM Supervisors.
Your pilot is also free to reach out to Mani for any clarification necessary (vatusa9@vatusa.net). Mani is a very approachable and helpful guy, and would be happy to clarify what happened from his perspective and offer any additional helpful tips as well.
Hope this helps; feel free to reach out to me if you need anything further at vatusa1@vatusa.net