When you say it shows 3 results, what do you mean exactly? Are you doing a search outside of the map and find 3 results?
When you search for layers to add to a web map, only items that are layers that reference services can be found and added from the search for layers option of the map viewer. There is also a checkbox on the Search for layers panel that says "within map area" which mean only layers that fall within the current map area will be listed. You may try unchecking this option of the layer you want is outside of the area you're currently looking at.
Thanks,
Mike