That is by design.
Only a single layout "lives" in memory at a time, and objects on a layout are loaded when the layout is loaded.
As soon as you go to a different layout, all objects/instances (except for those which are explicitly global in their properties) will be destroyed.
It is still not clear what exactly you are trying to do.
The big picture, "updating an object on a different layout" is the solution you decided was answering what you were trying to do.
What are you trying to do exactly ?