This occurs when the participant's person page is set to be "Private". If this was done by mistake, an admin can follow this path to make them visible again:
  1. Go to Fundraising > TeamRaiser
  2. Search for desired TeamRaiser and click Manage from the Actions column
  3. Search for the desired participant and click on their name
  4. On the participant record, in the information section on the right, click the blue button that says, "Make Public".
  5. Now the participant's name will be displayed in the Team Roster of their team and in the participant search results.
Tip: If you do not see the participant's name immediately, try clearing your browser's cache / delete browsing history, and then refresh the page a couple times.