You talking about the Nutty Putty Cave? I hate to break it to you, but they sealed the ‘get your body stuck upside’ part up.

https://en.wikipedia.org/wiki/Nutty_Putty_Cave

After rescuers concluded that it would be too dangerous to attempt to retrieve his body, the landowner and Jones’s family came to an agreement that the cave would be sealed, with the cave as his final resting place, and as a memorial to Jones. Explosives were used to collapse the ceiling in the Ed’s Push passageway of the cave close to where Jones’s body was. All entry points to the cave were permanently sealed by filling them with concrete, making the cave system inaccessible