Dat Ranked Series....

So I started a ranked series at silver 1... I won a game and lost a game duo queue with diglett.
Then I stopped playing ranked for a couple weeks and played a bunch of normal games and ARAM's.

I come back two weeks later and I'm not in a series but I'm at 100 LP.
I assume I have decayed, but thought it was strange that it happened so quickly.

However, I then proceed to play two ranked games. One win and one loss, but I'm still at 100 LP and not in a series.

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