The block I place down just wastes itself

The Block I place down wastes itself.
I was playing on SMP when I was just about to make a nether reactor.
But the Nether Reactor Core glitched into a powered Rail and the Core
was removed from my inventory and hotbar and didn't even drop
itself. We wasted three diamonds!!! All I wanted was to get some
loot from the Nether-tower-thingie.