Double Buff Glitch?

I was playing a game recently and I had gotten double from a kill. I had double buff on me for about 10 mins strait. It went off cool down where the buffs duration show. But stayed around my character and still slowed and gave me mana regen and everything. I never died, and it was there until the end of the game. It should of gone away but it never did. Has this happened to anyone else too?