If you follow the below link you should be able to merge your calendars or at least show both.
Let us know how it goes. Good luck.
You can also try running the switch outlook.exe /resetfolders to reset the default to its original heirarchy. (Close outlook, go to the run line and type the command. It will re-open outlook and resolve the folder issues.) You should then be able to delete the second calendar. I saw this same thing happen to one of my users and the resetfolders switch worked.