Yup, a deal gone wrong. I knew a guy who was in a similar situation. He was selling an item for a friend. The auction ended, the friend decided that he didn't want to sell the item at so "low" a price. I told the guy that it's his reputation that will suffer and the "friend" needs to understand the binding nature of a bid, regardless of the hit (or lack of profit) he takes on the deal.
As for what to do. Trying to work it out with the seller is the A number 1 first thing. No threats need to be made but everyone has to understand that there was an agreement and it was broken. Yes, he's gotta learn about responsibility and it's a shame you can't give feedback to the seller's friend.
As for what's obvious in the matter, I see a couple things. Money is tempting and it's very normal to deal with people with less than stellar integrity. Clear, negative feedback can be a good indicator of how the deal went foul. Especially since you aren't out any money on the deal, you essentially missed out on a hot deal. Also,
contacting safeharbor would be a very good thing, particularly because the listing fee he originally paid likely had been refunded, and he's getting out of paying a bit of the closing fee(s) by selling at a higher price.
I personally wouldn't call this a hot deal, though I could easily see it going into the realm of OffTopic (*shiver*). Take issues like this to the discussion boards on e-bay. You'll get attention. Not only that, but you'll get attention from people who want to help

If every e-bay buyer and seller was a professional we wouldn't run into problems like this. The problem is, that we (I apologize if I speak for more than just myself) assume too much. Go into every deal with your eyes open and have your sh*t together. No need to be arrogant or combative, just be clear. Clear and clean. (I think that'll be the name for my new line of cosmetics.

)