What is the irony in Guy de Maupassant's "A Piece of String"?

The supreme irony of Guy de Maupassant's short story, "The Piece
of String," is how, by a single, innocent act, a person's life and reputation can be forever
altered. When the thrifty Hauchecorne bends over to pick up a piece of string from the street, it
seems like such a simple reaction to a discarded item for which he may one day have a use. But
when he notices an "enemy," Malandain, observing him, he is ashamed that he has been caught
retrieving such a worthless item, and he exaggerates his actions. When another man's "pocketbook"
is reported lost, Malandain remembers Hauchecorne's suspicious movements in the street. Rumors
fly and soon everyone in the town believes that Hauchecorne has "found" the wallet. Even after
the pocketbook is later found--with money intact--Hauchecorne's guilt is presumed. Hauchecorne
continues to protest his innocence, but by this time, it is no use: The town has decided that it
was he who had found the wallet and later returned it for worry of prosecution. This simple act
haunts Hauchecorne to his grave, and on his deathbed, now a broken man, he exhorts how his life
has changed from just "... A little bit of string--a little bit of
string."