Intall Application from App Store - Strange Behavior

I didn't realize it, but I have all 9 pages of applications full. (I know, too many, but that's another thread!)

Anyway, I went to the App Store and tried to download another App. It "tried" to download, but it just returned to my Home Screen (presumably because there is no more room for Apps).

But here's the weird thing. If I return to the App Store, it shows that new App as "Insalled" (it is not).

So, did it put "something" on my Iphone. (If so, how do I take it off)? Or, is it just the App Store that is confused. If so, how do I "un-confuse" it?

 

GENIUS! I managed to find one amongst my 144 Apps that I could delete.

Reset the phone, and there appeared the new mystery App.

Thanks!!!