為什麼拾到錢卻變為盜竊? i did it the same case, plz help me

this case i did it is the same,so what am i gonna do, i dun mean that i want to took the money and i tried to find da man to give him back money , when i came out i cant find the man. i dunno how to handle the money and the next day i had to work so i just put it in my wallet. but now i'm so scared do i hv to go to jail or not ?