Would it be considered theft if I were to secretly retrieve what was stolen from me, after finding it in the possession of the thief who denied the theft?

It is permissible for a person to retrieve their money from someone who took it from them by theft, usurpation, or procrastination, without resorting to the judiciary, provided that they are certain that what they retrieved is their right, and that its retrieval will not lead to harm or discord, such as fighting, striking, or injuring, or being accused of theft. If they fear any of that, the matter should be referred to the competent authorities.