Are you using the #4 - "Search for Any Text" option? If so, you can limit the search to just WikiTree Categories by clicking the Categories radio button.
Also just to clarify, when I type in your "Space Rowley Sources" search phrase there and choose to search "All WikiTree Pages", I get a page with 4 advertisements (non-WikiTree) results and then the first 10 WikiTree results. If I click on page 2 of the results, I see the same thing, 4 ads, then the next 10 WikiTree results.
You may also be able to find Spaces and possibly even Categories that you have created/updated by accessing your contributions from your My WikiTree drop-down menu.