Complete Armature disappears when switching to "pose mode" /nothing is hidden, alt+h has no effect they show normal in "edit mode" but when i switch to "pose mode" or "object mode" they disappear and there is no "eye symbol" in outliner besides green Armature/Bone symbols. But there is a orange Armature symbol wich has eye symbol set to visible. Alt+H does nothing, no matter which mode i am in.

i moved a few of them and then switch mode for reasons, then i switched back to "pose mode" and they where dissapearing. I am very sure i hide nothing while these steps. I am using mac version 2.81a
i was able to do my pose while switching to "animation" tab and after i was done it seems they are apearing also in "pose mode" selected from "modeling".
Also could be caused by clicking another "layer" square on "outliner>pose then object data properties" but i am not sure.