Altivo

Yes, but when that happens it is usually with a great deal of fuss and fanfare. Mail sack found slipped down behind a cabinet or in a wall of the post office, for instance. I believe the rule in that case is that every single piece in the batch must be treated as registered mail, which forces an attempt to track down the addressee in every way possible. (A case like that made the news a few years ago, mail that had been delayed by accidentally hiding a mail sack from 1959 until some time in the 90s. They were able to still deliver about a fourth of it, 40 years late.