In 2012 Club Carlson ran a promo for a stay 1 night, get 1 night free.
I registered and stayed, but the free night never appeared in my account. Details of the promo are here, from the Flyertalk discussion. Some time after I qualified I checked to see if my night had appeared and it was missing. Correspondence with Club Carlson required me to send the confirmation email that I had registered for the promo. I couldn’t find this and so, as sometimes happens in the world of Miles and Points, I wrote it off.
The free night appears when you make a reservation by showing a ‘0’ points are required.
Yesterday I was happily looking for a night in San Francisco in August to use up some of my Club Carlson points, when I noticed the Magic Zero appear!
It seems that somehow the free night had been processed after all, and appeared as if by magic. If I had not tried this I would have lost the night. Now I am happily sitting on a free room in San Francisco.
Thanks Club Carlson. You might do well to check whether you have a free night waiting for you also.