After heading back to the npc to repot after training at the map "Forest of Golem", I noticed some of my golem block stacks had been replaced with Skelegon and Skelesaurus etc drops when I went to sell off the golem blocks. I don't know when they were replaced, it is also possible that they had been dropped and I just didn't notice.
they was probably looted by your pet when you were afk in FM, not for sure but that's what most probably happend
