Well. Right after getting out of a game I got a notification that I'm knocked down to gold 4 due to inactivity...I play regularly though. Here's a screenshot http://imgur.com/KHirt6D I've never been inactive in solo queue...
Riots ranked system that switched from flat MMR to hidden MMR+ LP is shit. Any vet can tell you that much. No one likes it. Anyone who says they enjoy playing promos is a fucking masochist or a liar. (or both in some instances..?)
Might be your 5's team that has been inactive.
EDIT: Nevermind. It says solo games.
You must have been at 0LP. I get that message too, but it never bumps me. The only time I am bumped is when I am at 0LP and I lose a few games.
Gold doesn't decay after inactivity any more. IIRC there's a bug where if you get demoted for a valid reason, it displays the wrong message (this one).
