new enderchest, create place, reset to spawn

I have done this three times now we started the world in 1.6.2 and found the nether fortress back then. We updated to 1.7.2 since then I have made 3 ender chest and time I place one in the nether fortress even if I pick it up when I log out and back in and am reset to spawn with nothing and now my ender chest are empty. Lost a lot of diamonds to this one. This is on a friends server...