OOC

In chronological order following happened:
1. Some time ago party accessed this tomb room already descending from LVL-1 "Devil Face & Tunnel to next floor down boat room". There is a shaft in the ceilings of the tomb and party used a rope back then, but rope is gone. See more in players notes for LVL-1.
That was also when party looted the dead dwarf. Vatoris stay in the room to do some investigation, nut the rest of the party afraid to step on the floor decide move along. Later party forget about Vatoris and do long rest in tiny hut without Vatoris.

2. Next day, while in lvl-2 (current floor) Nyx looked into this tomb through "Jackal's head". I suggest you look at the players notes for LVL-2 "Jackal's head" to learn what he saw. I was actually quite surprised no player had any questions about that Nyx saw. It was not my mistake that he did not saw Vatoris in there.

3. Now maybe some 20 minutes later you open the entrance by descending stone block into to floor.
You see the same tomb you been to and were not able to open golden sarcophagus, although you were standing next to it.

Nyx did not see Vatoris dead body through Jackal's head. Neither he saw him alive, but you see his dead body.

it is attached to stone block with Sovereign glue and you don't have access to neither wish spell nor magic items to break glue effect