We have a number of requests that don't show up if we search for them.
If we use the direct url with the request number we can get to the request number.
This is usually because the requested for user of those requests is inactive.
By default, requests for inactive users will not be returned in a search.
You can get these requests to show up by using advanced search and adding the search condition:
Requested For User Status - equals - inactive
Then add your search condition like:
Request ID - equals - 12345
(Where the number is your request ID).