I'm itchy about giving serial numbers to people I don't know. Thoughts?

Hello, everyone. I recently sold my rifle to a buyer. Over the course of the sale, there were a few people who asked to know the serial number. Out of the 60+ inquiries, I replied to about 50. I never gave out the serial number. it just didn't feel right giving serial numbers to people I didn't know, and I think those people could be up to no good. I sold my rifle to a friend of a friend, it worked out well, and I think the buyer was happy. I promise you that it was not a " indexPath" or anything like that. I'm curious to know your thoughts on this topic. I'm not sure if I'm itchy or justified. Thanks in advance for your input.