A long overdue followup:
We are the result of a bunch of transitions, all successful, from a lower-density energy source to a higher-density energy source. Many other societies which could not find a higher-density energy source ended up in overshoot and collapsed - but, of course, they aren't around to serve as a cautionary example.
There's not any guarantee that an economically feasible energy source even at petroleum's energy density is out there waiting for us. Nuclear + major battery improvements, for instance, doesn't even cut it; nor does anything using hydrogen as its energy store.
Physics trumps economics.
The term is survivorship bias and it usually arises in the world of finance, but has applications elsewhere. In short, if the things you're studying are those that survived previous transitions/calamities/events/whatever, you may either have an inaccurately high rating of the current 'survivors' or you may assume that all such transitions are successfully navigated.
In the Peak Oil case, this fallacy rears its ugly head as people bring up "well, we survived Peak Wood and Peak Horse and Peak Whale". But there were societies that did not survive, because they didn't find a higher-density energy substitute in time. We just don't hear about them, because they aren't AROUND anymore. They overshot their resources and didn't find an alternative, and they died out.