I thought it was something more like she was injured during the conflict, and now the complete information is lost. Roy will probably have to recreate it if he wants to use the ultimate flame alchemy, and he'll probably need it to kill off the Homunculus or some other external threat.
Yeah, poor Armstrong, made me feel really bad.
I found it interesting that Kimbley was actually somewhat sensible before, and he was driven mad with the power the stone provided him. His philosophy wasn't exactly the moral high ground, but he wasn't wrong. He looked very controlled, like he was keeping sane by not being horrified by it and not enjoying it. Simply performing his duty. Afterwards, we see how changed he was by using the stone.