I should mention that both the standard and wildcard tags both return search results, but the wildcard tag does not show up in the field discovery panel.
All of the following searches work:
Field Discovery Working:
Here's an example of a tag I've created which shows as a field in the format of tag::host.
Tag Name: QA
Field value pair: host=abcd.com
Field Discovery Not working:
When I add the wildcard to cover variations of the hostname i.e. short and long, the search works and returns results, but I do not see the field tag::host in the field discovery panel.