Confederate General Heth at Gettysburg - looking for shoes story?

I have been watching the movie Gettysburg. At first i thought that the story that Confederate General Heth moving into Gettysburg looking for shoes for his men, actually made sense. But the more i watch the movie, i am convinced that Heth literally 'bumped' into the Union army. In the absence of confederate cavalry, i think Heth ran into the union cavalry under Buford - who possible saw Heth first and ambushed him. So i wonder where did the story about searching for shoes come from and why its given any credence about why Heth went into Gettysburg.