Guy de Maupassant wrote often of the petty bourgeosis of whom Maitre Hauchecorne is one.  And, for this class, Maupassant had a certain disdain.  The tone of this disdain prevails in his short story, "The Piece of String."  M. Hauchecorne is so parsimonious that he stoops to pick up anything that can be useful.  One day, he stoops down with pain and retrieves a thin piece of yarn.  As he starts to straighten himself, he detects that his enemy, Maitre Malandain, has caught sight of him:

M. Hauchecorne felt a bit humiliated at having been seen by his enemy scrabbling in the dirt for a bit of yarn.

Because he does not wish M. Malandain to think him so poor that he must stoop for string, M. Hauchecorne feigns that he "is searching the ground for something he had lost."  M. Hauchecorne is a man who takes pride in having made a sound business deal. He is very conservative, yet he does not wish to be thought of as having need of this conservatism, or of being somewhat obssessive. 

When Hauchecorne is seen picking up the piece of string (by his enemy), he reacts by pretending that he is continuing to look around for something else on the ground. He does this because he is ashamed.

To me, what is unusual about this is that he really should not be ashamed.  According to the narrator, all "true Normans" should act as he has done.  So why is he so embarrassed?

In my opinion, this shows that he is a very proud and sensitive man.  He is so sensitive that he cannot bear the thought that his enemy will have a reason to look down on him.