If you save a scene with a clothing item having Hide Material active, then something in the scene triggers hide material off, the clothing item appears at 0,0,0 in a default pose, not where the atom wearing the item is currently. It only happens if the scene is saved with hide material active. If the scene is saved with hide off, then you can hide and unhide normally. It's only when the scene loads up with something in the hidden state. Demo scene attached.