Objects don't show up in the screen layout I have several screen layouts that I have defined:  default, animation, UV, etc.  

In some of them, after working in the layout for some time, some of my objects disappear from the scene, and won't show even if I unhide them.  They still show up in other screen layouts and in my outliner.  I assume I'm hitting a button or something, and it's not random, but I haven't been able to figure out what I'm pressing.  I have been able to get around this by deleting my screen layouts and remaking them, but I'm getting tired of doing this.  The objects are all on the same layer, and they won't show up even when I render.  

Does anyone know what's happening?
you might of hit H and they are hidden. check this by going to the outliner and seeing if there is a eye beside the object if not click where the eye should be or press alt h in 3d view. also check that the two other icons are visible in the outliner.