Question

Good evening, Rabbi.
A story that happened to me… I was called to a house in order to catch a snake. It turned out to be a pet snake (a snake that does not exist in the wild in Israel). This was in the Ramot neighborhood in Jerusalem. I asked the person at whose house I found it to post a lost-property notice in the neighborhood WhatsApp group. A young man / kid contacted me and described that he raises snakes and that many of them escaped from him this year, and he sent a picture of the snake that I supposedly found. It had escaped from him 3 months ago. Can we assume that he gave up hope of recovering it and I can keep it, or is one obligated to return it?
And also, how do I know that it is his with 100% certainty? Maybe it escaped from a friend and he is using his pictures?
Thank you very much in advance.