Salem

I start to build ore smelter, filled it with 3 bars of iron and 10 hayes.
Then a went to forest, and when i returned there was no building pillar
Why it happened?
My land is surrounded by split-rail fence with lock so no one had chance destroy it

was it on claimed land?

What hes saying is that on claimed land things don't decay. If not on claimed lands, things will decay and eventually disappear. Some faster than others.