Snail Mail

I recieved a letter from a customer today that was posted 1st class on the 28th June, this was a franked, (not stamped letter) typed envelope not a scrawled spider of an envelope.
why did it take this long to reach me?
it travelled approx 35 miles which sort of implies it has been sat on a bag somewhere or maybe in a box or cupboard. pretty poor service whatever the reason.