Perhaps not, but it needed to be found. Also, the gamma rates (by which, I presume you mean the gamma-gamma decay branch) aren't the only thing of interest.
Alternatively, why should there be nothing rather than something? Nothingness is hugely unstable. It only takes the smallest drop of something to ruin it and we know that "somethings" can appear and disappear quite happily.
True. I'd like to credit the readers of this forum with a modicum of intelligence though. Enough to make the distinction.