Gameplay

I was playing all for one and we were all Mordekaiser. I had just killed an Ezreal with ult and had his ghost clone with me, I was going back to base and I alt tabbed to check something right as the backing animation finished and I was teleported to base. The game froze for a second then it alt tabbed, when I alt tabbed back into the game the client refused to go full screen and was windowed slightly. I also had control of my Ezreal clone instead of Mordekaiser and couldn't move my Morde at all. Restarting the game and loading back in fixed the control issue but my client still refuses to go full screen. I couldn't find a post about this in the boards but has anyone else heard of this or a way to fix it?