Default Help Needed! Fix phone on Mac?

Could anyone tell me if there is a way to fix my verizon lg g2 running 12b? I tried to restore a rom from twrp yesterday and it would only flash the lg screen for a split second. I can't get into dl mode either. I only have a macbook air on me so I can;t really do much. Does anybody know any method to fix my g2? Also, if there is no fix, is there anyway for lg to tell if I was rooted if I sent it into verizon?