Agree to all the aforementioned.
I’ve been to the small park on that spot & in the Chapelle Expiatoire. Climbing down from ground level, you are led to a small subterranean room that houses a stone sarcophagus, which it is said now contains earth that surrounded the remains of the king’s casket. There are also dried, long-dead floral arrangements placed in small wall niches flanking the sarcophagus. It indicates that the floral tributes were from the early 19th-century when the Chapelle was dedicated.
The Queen wasn’t provided a coffin, just thrown into the dirt. Not much physically could’ve remained of either of them, what with decomposition, the elements & the liberal use of quicklime. They said that a courtier recognized the Queen’s mouth when her head was exhumed, but that was probably wishful thinking. They said there was also a garter in the grave. Whatever-it was all scooped up & reburied at St. Denis.
They were never in mass graves, just unmarked.