I have only seen that once in the fighters guild base where they have the forge thing.
Interesting, I have only seen one and this was in pvp with guild and everybody saw it, if its goes away its sounds more like an client issue in the game or graphic card messed up loading the model.The 'missing' items in game are quite normal, you can see them in some games that have been launched years ago. I remember the funniest I saw was in SWTOR where you have pets too, one of my guildies R2D2 look-a-like robot pet was actually in correct form what it should've been but it just said 'missing' all over. And that last for days
Funniest in this game that I saw was my husband's dragonknight character had a square shaped 'missing' box around his torso. After drinking beer that night and laughing my ass off at it I failed to take a screen shot cos it disappeared after a couple of minutes