Bought back is the auction room jargon, what it means is that the skin was offered in the live auction room nobody met the auctioneers limit and now it will be in the private treaty catalogue. Sometimes the buyer has to contact his customer before they can try and match the price the auction house was asking for the skin.
Also the following link explains the way the exchange rate is set
http://www.nafa.ca/nafa-exchange-rates/