I was playing blitzcrank and I randomly died

I was at full health then A brand ignited me and hit me with a q. I walked away and was at half health. All of a sudden my mana sheild passive popped maybe from brands passive. When my mana sheild ended I died to brand. It was a good 10 seconds or so after brand had done any damage and I was nowhere near brand at all. I didn't have any dots on me either because I was recalling. I know it wasn't a enemy champion because my team had just got an ace. Wtf is this.