A list of important theological topics that are rarely mentioned in Scripture:
- The Lord's Supper
- Ark of the Covenant in the New Testament
- The land of Israel in the New Testament
- The three persons of God in the Old Testament
- Resurrection and final judgement in Old Testament
- The future shape of resurrected world in either Testaments
- Eden, Adam and Original Sin
- ... have I missed any?
I think this supports the idea that the location of a theological topic in the biblical narrative is just as important as frequency or quantity of mentions.