This is a bug related to the feature for restricting request types that is in EAP as described in the documentation below:

https://support.atlassian.com/jira-service-management-cloud/docs/add-or-remove-restrictions-on-request-types/

The restricted request types should not be available when searching on the portal and it has been observed that the search results display such restricted request types as well. The user gets a Not found page when attempting to access the request type from the search result and so the functionality works, but it would be best to not show the restricted request types in the search results.