Since the 4th century there has been a church were Christians believe the tomb of Jesus Christ is, yet we all know He was Resurrected. The Church has never said that the Blessed Mother didn't die.
And they never said she did
The Extent of the Magisterial Teaching
In defining the Assumption as a revealed dogma, Pope Pius XII did not infallibly answer all the questions that relate to the “where, when, and how” of the Assumption. For example, we do not know how old Mary was and whom she was with at the time. Also, the Holy Father did not attempt to resolve the controversy as to whether she was in Ephesus or Jerusalem, as there was no mention of where she was at the time of her Assumption. In addition, Pope Pius XII’s definition said nothing about Mary’s mediation, her queenship, or other privileges.
And significantly, Pope Pius XII left open the question of whether Mary “died.” Note that the definition intentionally uses the ambiguous phraseology, “having completed the course of her earthly life.” Some maintain that she did not die, because her Immaculate Conception freed her from the effects of original sin, including death.