Tibbers Stole My Blue :(

Yesterday I was playing a ranked game on my Main Annie and it was about 18min into the game I got my blue buff (solo) and used tibbers to tank it and kill it as my health was fairly low. Tibbers killed it and no other champs were even in the same quadrant as me, however the blue buff didn't appear on my champion, or tibbers for that matter. It simply disappeared. I have killed blue wit tibbers before and it has given Annie the blue buff, any help would be great. In that particular game not having it didntcause a major issue, but it would of certainly been an easier 3 min of fighting.