the third conditional is used for a past situation that didn‘t happen.
If I had paid attention…
In other words, in the past he did not pay attention. The past situation that did not happen is: Finn paying attention. That‘s the part we call the conditional clause, or the if clause. Next we have the result:
… I wouldn‘t have got lost
This is the result of the past situation! It‘s the result clause or the main clause. Finn did get lost, but if the past was different, he wouldn‘t have got lost.
ex:If you hadn‘t watched our video, you wouldn‘t have seen Finn in an embarrassing situation!
原文：http://www.cnblogs.com/a-n-dy/p/5403214.html