When Anton goes to his friends house at the beginning of the movie to get pot, he sees his dream girl ride by. When his friend suggested that he should wear pants, he slips out the window with no shoes on then when he picks up the lyrics book he has shoes on.
if you look closely, you can see that he put the shoes out the window before he climbs out. just because you don't see someone do something doesn't mean it didn't happen, the camera missed a few minutes of time where he could've put on the shoes.
You must be blind, cuz it isn't hard to see. He's in his bare feet in the house and then when he leaves he puts the shoes out the window and puts them on when the camera didn't see!