Yris wrote:Castle belongs to my clan
It might be that while you were gone your clan lost control of that castle for a while, did not control it for several days or longer and then have retaken the control again. That way you would have lost the castle equipment in the process.
Another possibility is that the clan leader has an option to "reset" castle equipment. That means that all the equipment that has been given out to the members disappears and new items spawn at the castle NPC. This is being used because the number of the castle gear is limited and if there are a lot of inactive players (as you mentioned you were one of them) who have castle gear on them, but do not play and do not use it, they are literally screwing all the clan as those who do play, can't get the gear. In that case clan leader resets the gear and redistributes it to active players.
You should ask your clan leader about those things and most probably he'll confirm that one of those two scenarios have taken place.