>>291203558
>Where did those go?
I have no idea, and I hate it. What you should do instead of double clicking them is drag them to the scene list and it will be there among the other scenes like normal. 
>Also why are some of these models in the scene greyed out and how do I make them not greyed out?
They're probably inactive. If you click on one of them and then go to the top right where the inspector is you should see the a box next to the name of the model, if it's inactive it's unchecked. Simply just check it and the model should be visable in the scene again.