Thanks for pointing this out. The Search Listings option on the current default Saved Listings page is actually designed to operate independently of any other filters on the page, including those you mentioned, so most of the behavior you have described seeing here is to be expected.
However, the new version of the Saved Listings page which can be accessed by clicking the “Try out our new and improved Saved Listings page!" link on the default version of the Saved Listings page was designed to take these filters into account when the Search feature is used so you may prefer using that version of the page instead.
For example, if you search for a keyword on the new version of the Saved Listings page, enable the “Fixed Price” filter and then select “30” from the “Listings from last ___ days” menu, you should only see the items which match your keyword search AND correspond with those other filters.
I am not sure what would cause a completely unrelated item to be returned when you search for a specific item though so, if you need further assistance with that particular issue, we would need to look into the specifics of that behavior on an individual basis.
I hope this helps. If you need any further assistance wit this functionality, please contact our Customer Support team by mousing over the “Help” tab within your account and selecting the “File Support Case” option.