I had a similiar thing happen to me the other day. About half way to work, about 7 miles out, I realized I was lidless. I continued to ride and even rode home without it.
My concern was my kids. We have rules about riding and one of them is you must wear your helmet. And I broke the rule. I was more concerned about setting a good example then getting hurt. I guess next time they forget something I might be a little more understanding.
I think you did the right thing.
Dave