You also have two options in that window to "Highlight matching items" OR to "Hide non-matching items". (The latter is going to be easier for you if you have a lot of items on the farm.). Then click the green check mark. All matching items for your search should then be showing, either highlighted or the only things showing on your farm, depending on your choice. When you are done, click on "Show Items" bottom right of your game screen and the rest of your items will be shown again.