Thanks for sharing, @agw.
That reminds me of a time I fell into the regression testing complacency trap. I wonder if there’s a bias name for it. 
The sales team rushed into our office to point out that ad revenue had suddenly taken a dip. Turns out myself and my fellow testing colleague had signed off a release without realising all the AdSense had disappeared. Both of us were so used to running regression that we no longer used the regression test checklist. We literally didn’t see what wasn’t in front of us – the missing AdSense. Was a big learning day for us both!
We resolved the issue quickly and through a post-mortem, it actually led to a push for automated checks for the essential features and a renewed energy of not taking things for granted or becoming complacent with regression tests. On reflection, it was very likely the start of moving towards a whole-team approach to quality instead of relying on QA folks to sign off a release.