Q: Can a funeral mass be held without a body or cremains present as in the instance where the body was interred after death and now the family wants to have a mass.
A: Yes, indeed. In fact, that is what should happen in this circumstance.
In the case of cremation, the appendix to the Order of Christian Funerals in the United States treats this in 423-424. It’s the second of three options.
The same could happen with a body present. Paragraph 6 of the Introduction to the Order of Christian Funerals calls for a Mass after interment if one did not happen before. You’ll find the introduction in the back of that book instead of the front.