Sketch lost after reboot. Uno Throughole

hi i have uno throughole version, i dont know my serial but when i unplug and plug back USB sketch gets lost :( I saw post about same issue with SMD version, i dont remember where i bough my unit, it was long tome ago. I do have AVR ICSP flasher (i have no idea how to use it) but if i get hex boot-loader will that help?