I had never heard of a "sheepfold" before so I looked it up. A sheepfold is just like a sheep pen. Like without a roof and usually just a few feet high. Either the article used the word incorrectly or there is a ton they are leaving out here. Maybe it had something to do with his captors magic spell?
It could be that the sheepfold concealed an entrance to an underground cellar? There are several parts of this story that are not easily understood by us outsiders.