Sheep got out, didn't think it was possible

I was sure I had it covered this time.  I think they pushed on the lower movable fence over the almost dry creek. One of the momma sheep with her two babies was up wandering the hillside.  Of course she is teaching them bad habits.  Luckily, one of them is going to be food eventually.  Sarah is outside chopping down thistles in our yard again.  She thought she was done yesterday.  Not so much.  I will go check on the sheep and see what I can do about them sneaking out.  I really did think I had it covered.