Presumably it was a flanged bolt-head, the type with a kind of integral washer?
Otherwise couldn't you have slid the ratchet spanner down the bolt and off the head, and then screwed it in a little with an open-ended?
You presume right. Even if it wasn't, it still wouldn't have screwed back in. In retrospect, I don't think the bolt is meant to come right out anyway because it has bleed holes round the edge that the oil comes out of when partially unscrewed.