I've had similar: Steam Message "we've come up empty". No trace of COD.in Steam library. Steam have replied to my enquiry. I have to send them photos of the game box both inside & out as well as the leaflet with the rego. number before they'll help. All that when I'm supposed to be registered with them. No more STEAM-dependent sims for me!
Pete.

Did you get it resolved at the end Pete? How long did you have to wait for them to reply?

"We've come up empty"
 

No Matty - problem persists. I tried to send them photographic proof of ownership as requested but got no acknowledgement. Same message shows up every time. I've been frozen out for about 10 days now! I seem to have run out of options.
Pete

in my experience with Steam support they suck bigtime.

Emailed photo of my cd key + other numbers to them as well. It has been two weeks now. Have you tried to reinstall STEAM or ClOD?

Reinstalled Steam and tried to reinstall ClOD as well - unfortunately got Duplicate Product Code message so no go. Steam apparently needs more time to investigate further...tbc...

Finally - Clod is available again. Still wandering what has actually happened - STEAM support didn't offer any explanation. Glad it's all sorted now though.

What a drama! Glad it was eventually sorted out for you. Events like this can't be good for their reputation!

Cheers!