In the layout editor, if you use standard layout, on the right you have a window. In that window you can show Layers, Projects but also Objects. Choose it to display the project. Find your object, drag it to the layout.
If you want to completely delete 'the last object', then you do that also in that window under the rightclick on that object.
Also, when you have objects showing, you can rightclick that window to filter the objects, all objects for the whole project, or only objects in the current layout. This might be a help to know wich objects are in a layout.