We've had at the Commons recently several cases where uploads were not done completely. The images showed up, the file history showed even the full upload summary, but the corresponding image description pages were not created. As a result, if the user used the license dropdown to specify the license, that license was lost completely (because it doesn't show up in the upload summary).
An example is http://commons.wikimedia.org/wiki/Image:Palencia_-_San_Pablo_15.JPG the image page was created manually on the day after the upload, see the page history at http://commons.wikimedia.org/w/index.php?title=Image:Palencia_-_San_Pablo_15.JPG&action=history . The uploader was notified and did add the license after that, so all is well for this image now. But there are other such images where the licenses were lost, and where the uploaders did not react.
I've observed this behavior twice so far, once on July 31 from about 10:30 to 11:50 UTC, and now on August 31 from 17:19 to 17:39 UTC.
See also http://commons.wikimedia.org/wiki/Commons:Administrators%27_noticeboard/Archive_10#Server_hiccups and http://commons.wikimedia.org/w/index.php?title=Commons:Administrators%27_noticeboard/Attention&oldid=14027516#Problems_with_upload
T63898 (restricted task)
T34551: Descriptionless files (Missing page_latest referential integrity issue)