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human
[Breaking Bad] How exactly did Mike find Heisenberg?

In season 2 episode 8 of Breaking Bad, Walt meets with Saul Goodman for the first time. Jesse and Walt eventually pay Saul to set up Jimmy "In and out" to take the fall while pretending to be Heisenberg. Afterwards, Saul unexpectedly visits Walt at the school where he was a teacher. Walt is shocked that Saul figured out who he was. Saul says it was remarkably easy, as he paid his PI for 3 hours, which means it probably didn't take more than one. 

I don't know if it's ever explicitly stated, but I'm assuming the PI was Mike. So how did Mike figure out who Heisenberg was so fast? If I recall correctly, the only clues were a description of what Walt looks like, as well as Jesse, the fact that Walt had a bad cough, and that he was remarkably talented at making meth. 

I know Mike is good at what he does, but how would he figure it out within one hour?
gpt
Probably searched local chemists in the area. Then looked at any that didn't live in upscale areas or were employed by any major well paying jobs. If that wasn't narrowed down to just Walter then he probably either looked for any recent medical expenses and inquiries. Or simply found a snitch that knew Jesse and worked backwards based on the description of Walt and the knowledge that he was a chemist. Walt being a Nobel chemist and having a son with disabilities makes him stick out as a giant red flag for possible corruption or illicit activities to anyone with half a brain for why people will break bad as the term goes.