...is not evidence of absense! This is definitely true when it comes to bugs. We could spend a year and not prove that X-Plane is bug free, but it only takes a minute to prove that it has bugs.
(This isn't unlike an NP-complete problem like prime number factoring; the asymmetry of proof provides the protection.)
Can you tell I've been reading "The Black Swan"? A book that's very relevant financially these days. Perhaps the tragedy of the housing bubble is that it moved everyone's houses from Mediocristan to Extremistan* without the people that owned the houses (that'd be all of us) noticing. Or perhaps we've been in Extremistan for a long time and just didn't realize.
* (These are Taleb's made up names for systems that experience the law of big numbers vs. systems that experience chaotic outlier events.)