How is the problem solved?

M. Loisel solved his problem by advising her to request her friend, Mme Forestier to lend her some jewels. Accordingly, she went to Mme Forestier and borrowed a diamond necklace for the occassion.

They waited for a week to find the necklace. Eventually, they could not find it and decided to replace it. They went to a shop of the Palais-Royal where they found a chaplet of diamonds, which seemed to them exactly like the one they had lost. They bought it for thirty-six thousand dollars.