I'm developing an eyetwitch. Revenge for your friend, for what happened to her. It takes longer explaining this than it probably will killing the person before she unleashes who knows what on the general populace. I hope it's terrifying and deadly. The higher the body count, the better.
If we were able to track it in Soul Society, we would have known Aizen's every location, and every time he so much as sneezed. It didn't work like that and it doesn't in this world, either. The energy I have found is of her signature, which my associate isolated during the attack. But I have not the time or the inclination to spell out every fine detail of my scientific work to you.
The location is where I listed it, above. If you show up and live through whatever happens, I suppose that's acceptable. If not, then I will be dragging what's left of you back to the lab, to use as various tissue-based test samples.
As for 'shouldn't you idiots be able to track it'...let's see you create something better, substitute soul reaper. I highly doubt you could manage making a clock with a potato battery, even if I handed you a kit with picture instructions.