Is it permissible to take compensation from the seller after the theft of purchases left in his custody?

If the merchant with whom you deposited your goods claims they were stolen, then consider the following:

1. If the merchant did not neglect the safekeeping of the trust: He is not liable for it; because a trustworthy hand is not liable except through transgression or negligence. He is to be believed under oath regarding his claim that the trust was destroyed, even if he mentions a hidden cause like theft.

2. If the merchant neglected the safekeeping of the trust until it was stolen: He is liable for it and must give you a similar item if it is quantifiable by measure, weight, or count (mithli), or its value if it is non-quantifiable (qimi). This is because negligence in trusts that leads to their destruction necessitates liability.