The basic law (Megillah 31b) is to read the Torah sequentially, but occasionally the sequence is interrupted (such as on Yom Tov) and then resumed. All other breaking points are entirely customary.
Historically some communities read sequentially to finish the Torah every 3 or so years, and others read to finish every year. The latter one is the widespread custom nowadays. To accomplish this, each community combines or splits various customary sections at various times as necessary into a new single reading for that week (with only seven readers and one haftara) to meet that community's goal.
Accordingly, the only way someone who always attends synagogue would miss any verses is according to some minority opinions that prohibit getting through (or what they call "catching up") too many customary sections at once (see here) for certain hard to understand reasons. But that is a minority opinion applied to a very rare case.
(Note nowadays, nearly everyone follows one of 2 or 3 common sequences of how to combine and split the sections to accomplish this, and ad hoc rearrangements are incredibly rare.)