Just got this quest from that totally racist elf, and so the map arrows tell me to break into the guy's house and find something in his Chest. Though when I lockpick the chest and open it, I only get some gold and a wooden plate. I take everything, hoping to move on to the next part of the Quest. But apparently that wasn't what I was supposed to take.
I kill Ogmund and check the chest again, and there pop's up Ogmund's Talos amulet, but I fail the quest. I'm guessing that's what I was originally supposed to take, but it's not spawning correctly.

Some more info, I got to Markarth through the Whiterun drinking game. And I already broke out of Cidhna Mine and sided with Madanach. I also saved Margaret from the attack in the front of the Mararth Market.

Anyone know the item ID of Ogmund's Talos Amulet so I can spawn it in the chest via console?

No sorry but I did find it in the chest when I snuck into his house late at night and he was sleeping on the bed. Did you break in during the day? Or you could try to pickpocket it off of him. Questmarker could be wrong though for daytime attempts to steal it.

Also unless you are roleplaying an altmer it is more enjoyable IMO to accept the quest then sneak around inside the keep and assassinate the three thalmor lol.