Weapon turns up as Item not found

My weapon, which I unequipped to equip a lance for the argent tournament daily quests wont let me equip it. Its a black box with a red question mark in it, and when I try to equip it, it says "item not found" this happened after equipping my lance and has been this way since yesterday.

I opened a ticket to solve this issue, the GM left a response telling me to log completely out of WoW, open the WoW file, rename cache/interface/wtf to cache-old interface-old and wtf-old. I did this, then restarted my computer as instructed and logged back into WoW, nothing had changed..cept my addons wheren't there. I have no interface altering addons and I use the regular WoW launcher. After clicking "need more help" I was instructed to look at Faqs, which I found to give me no help, and contact blizzard tech by phone or e-mail.

I decided to see if the forums could help before I sat for 3 hours on a phone.