Mary certainly has no grave. That is very telling.
It sure is. It tells me that no one felt it important enough to record even her death.
You Catholics cannot seriously think that any true Bible understanding person would take that as a basis for the importance you give Mary. Not once is she mentioned after Jesus ascension into heaven and you make her as important and in some cases more important then Jesus. That is preposterous.
Not only is the veneration you give Mary not scriptural it is anti scriptural.
It's very meaningless.
Her having a grave might be able to prove that she died. Not being able to find it means nothing other that nobody has been able to find it.