He didn’t after Robert left Rumple threw the hair on the ground and said something like small items can mean big things in that sarcastic tone of voice. He was just putting on a show because he saw himself in Robert.
Rumpel’s actions in that scene also suggest that Robert did not really have true love in his life — not true romantic love with Ruth, nor true parental love for the boys — otherwise Rumpel should have kept the hair for a backup of the true love hair spell.
Maybe a person has to be oblivious to personal guilt, like Charming and Snow, in order for his or her love to be pure.
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