Blocks and Items deleted from End spawn room when gamer leaves End and returns.

Possibly WAI but wiki page on "The End" should reflect that if so.

Any blocks/items placed in the The End spawn room after entering the End Portal will be deleted when the gamer re-enters the overworld and further enters The End again.

Easily recreated, enter End portal, place block in room, re-enter overworld via portal, re-enter The End via portal, placed block has been deleted.