Paul, the earliest source, never mentions an empty tomb. If it were part of the earliest tradition, wouldn’t he have said so?

Paul never narrates any details of Jesus’s life beyond the creed, so his silence about the tomb is silence about everything, not a specific gap. And the creed he quotes says buried and then raised, a sequence that meant, to a first-century Jew, that the buried body came out of the grave. His argument in 1 Corinthians 15:35 to 54 about what kind of body is raised presupposes that resurrection involves the body that died. The empty tomb is implied rather than stated, which is not the same as absent.