They wouldn’t make public even if they did know where her remains were. Can you imagine the havoc that would cause?
Ask that feller or gal to prove the RCC hasn’t secreted her remains. Doesn’t it seem to you that early Christians might have noted the day, date, and sundial time that Mary was assumed ANYWHERE had they seen her caught up in glory?
Mary the mother of Jesus is still dead, or asleep in the Lord if one prefers, as is mine own, waiting on the next Resurrection. Cannot hear anything right now, much less prayers to her or in her name.
There is no proof or disproof of this discussion just now. It is strictly a matter of faith in and love of the Lord Jesus Christ and following Him alone. The truth, in His time, will be made evident to everyone who has ever had a tongue to confess or a knee to bow.