This is also a known issue if you have a FlyingBlue account and you pull up a booking there while logged in -- it will overwrite the record with your FB#. I also found this out the hard way, and was only able to reverse it with the help of an awesome CS supervisor via Twitter (this was a year or two ago) so unfortunately I don't have any good advice as to how to reproduce this result. Up until that point, it was definitely hair-pullingly frustrating as DL originally told me they would credit me with the flights but only after I contact FB and have them reverse it from their side, and when I did that FB told me "we don't do that anymore lol you're screwed"