A couple of weeks ago we had a route that got pivoted because the regular was off.  It just so happens that mail volume was really low that day.  Well one of the carriers was carrying a relay on this route and she was out there at like 8:30 AM.  One particular lady had outgoing mail sitting in her box but no mail to be delivered.  The carrier went and grabbed her outgoing mail and went on her way.  Well it just so happens that the regular doesn't get to the particular area until after 12.  So the lady, noticing that her outgoing mail was no longer in her box, freaked out.  She called the cops, the postal inspectors, and her bank and cancelled her checking account.  She then proceeded to call the Post Office (first place I would have called) and was told her carrier was off and somebody else delivered that street.  Because of the low mail volume she was there super early.  Imagine how that customer felt.