Okay so you have played the campaign (finished campaign) and now see you are at 24/26 missions or 25/26 missions – obviously there is one mission missing, the secret mission.
By now you have researched on Google how to get this mission and you have launched the mission “Media Blitz” and directed the Odin to the bottom right map corner and destroyed the building (looks like science building from Starcraft 1). Then you have picked up the documents and it reads “Secret found” – however, some 20 minutes later you have finished the map and it turns out that you cannot access the secret mission! What gives? Apparently when you have completed the campaign already the secret mission does not show. Here is how to fix this situation: as I have just done it and provide you with the screenshots, you can be assured that it DID work. If it does not work for you, then it either something went wrong or you are loading the wrong savegame/mixed something up.
This how-to is for Mac (OS X, Snow Leopard, 10.6) only, but I am quite sure something similar exists for Windows (PC):
1. Go to the folder /Users/MAC USERNAME/Documents/Blizzard/StarCraft%20II/Accounts/RANDOM NUMBER/ANOTHER RANDOM NUMBER/Saves/Unsaved/
2. Scroll down until you find one of the media blitz save games.
3. Copy it
4. Go to /Users/MAC USERNAME/Documents/Blizzard/StarCraft%20II/Accounts/RANDOM NUMBER/ANOTHER RANDOM NUMBER/Saves/Campaign/
5. Paste the file
6. Open SC2
7. Load the save file you just copied over from the CAMPAIGN tab, nothing else – make a mental note of the time (so you dont end up opening the wrong file).
8. Play the level “Media Blitz” again to get the secret documents.
9. Finish the mission, click on “continue”
10. Back on the “bridge” click the Starmap
11. Play the secret mission.
More details at IGN
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