Hurray the English language! In this instance 'by accident' would mean the person was not actively TRYING to find a way to bypass the lock screen, rather that he happened across it while doing something else. They did not use the term 'accident' to imply the guy dropped his phone and it unlocked. That the entire process involves a few steps does not invalidate that it was discovered 'by accident'.

Example: Post-It Note glue and WD-40 were so totally the intended results and not 'discovered by accident' while trying to create a completely different chemical than what resulted in their experiments so we should just ignore those inventions entirely and downplay their significance cause the inventor didn't just combine two chemicals together and snap his fingers to make something appear but because they both involve a complicated process of multiple steps they couldn't possibly have been discovered by accident.