My thinking is that his pancreas kicked in for a while. This usually isn't an on/off thing, but it "wakes up" and helps keep the levels down even after the insulin is gone. Then it "gets tired" and the fact that the insulin is gone raises the levels. But that it is waking up is great news. It may help in starts and stops but eventually it should work continually. Supporting it with small frequent meals and small doses as needed is a good plan.