Same here its been two days since my Nokia Collections Magically disappeared :(
I don't really "NEED" it but for some reason it just bothers me not to have it!
Same here, I'm not hurting without it at the moment. However I noticed it was gone and hope it comes back soon. Maybe they are doing something because of the impending release of a bunch of exclusive apps?
I have been in contact with Nokia and they said they were looking in to the issue. Obviously a master reset will bring the official Nokia Collection back to Marketplace. With news that Nokia has branded the Marketplace differently on Tango, I wonder if that has anything to do with it. I'm not too worried about it since I can still search for Nokia Corporation and get their list of apps that way.
I will report back if I hear anything more from them.
Had this issue with my 900 after an update. Didn't show up in Marketplace and nothing in searches.
So I found this on the Nokia forums, they told the user to open the Xbox Live app and wait until it finishes "updating" and you can actually see your avatar (swipe to right). Then you should see Nokia Collection on the 1at page of Marketplace.
This worked for me. After going letting Xbox Live load and looked at the avatar I went back to Marketplace and there it is right under AT&T Featured (for me) and above "apps". I'm on AT&T in the U.S..
Frankly they have such a nice selection of extras I was blown away.