No matter what the seller told you--- I'm guessing they knowingly screwed you. I mean, the seller was smart enough to strip all the parts off the frame except the trahed Mavic BB-- most likely they put them on a dfferent, undamaged frame. And sold the unwanted frame to you. This is the classic EBAY pump and dump. But doing anything about it will not by the easiest to get done.
Here's what I would do.
1. Clean the frame and look for more damage. Take your time and make sure the frame isn't total a total loss.
2. If the frame is undamaged, order the Stronglight theadless BB linked to above. I've never seen one, but Stronglight is a darn good company. The engineering behind it should work. Heck, order a new Stronglight headset while your at it...very nice stuff. After you do all this-- you're on your way to building a nice touring bike.