dissapearance of my minecraft

hoiiii, sorry if i make mistakes, im french, so, i wanted to say, i bought minecraft and played it for hours and then, my pc got a problem, so i contacted someone that is good at informatics and he rebooted my pc, like cleaned it completely as if he was a new and when i tried to download back my minecraft, they asked me to buy it again!!! i tried other accounts of my family to see if i bought it on the wrong account , they told me no, and i dont want to buy it again!!