Running - mixed results

Willow can run with me and can heel beautifully most of the time (off lead). I can make her down and go and wait and heel. The only thing is if you loose concentration too long she can dissapear off for minutes. This worries me because there are sheep in some of the fields near the woods I go in. I have tacken to making her heel with me near the sheep field, and go on after. She likes the game. When she does dissappear no end of shouting gets her back. Maybe she is not too far away in a down (her universal reaction to unknown shouted commands). I still need better recall from her, even when she is having fun. Unfortunately when she is in the woods she cannot see the point of eating, so although in classes she is a foodie, other times there is no reaction. She will come if you call and threaten to throw a stick. I am trying to teach her the touch command where in order to get something she has to come and put her nose to the palm of my hand. Hopefully if she does this at home she will still do it in the woods despite the non-interest in food.