There have been numerous reports on the PS4 of items, structures, and entire buildings disappearing without the purge being involved, often in single player offline. Here (1) are (2) some (3) examples (4). When you can hear building pieces breaking, that means it is a different bug than the one where a building simply vanishes, and instead is related to building stability issues. Most of the people whose structures vanished had the decay system turned off and did not have a full purge meter or had purges turned off, ruling those out.