It's not a glitch, that's how I had to design them because it's technically a brand new weapon and you can't create new weapons. Because they aren't technically a weapon, you were able to pull them out in Elysium allowing you to fight NPCs that you aren't supposed too which would break the game. So, the only solution was to take them out of the players inventory each time he enters Elysium and then give them back when he leaves. Kind've like, leave your weapons at the door kind've thing.
As far as Daimoinon 5 and Serpentis 3, you get new weapons when using those powers, claws respectively. So, those Vukodlak fists get pushed aside when using those powers to make room for the new fists.
In case the Vukodlak fists don't automatically re-equip you can always hotkey them, which is what it appears you did.