I'm the leading bidder on an item that has received multiple bids and there is less than 12 hours left when suddenly it is listed as sold for a much lower price. What happened? Is it allowed? Should I report it?

I bid on two items ending concurrently from the same seller (not the guy above) and lose both auctions. Immediately I receive "2nd chance" offers to buy them at my maximum bid. Obviously shrill bidding is going on. One item I bought (because I needed it), the other I did not........but should I report the seller? Will it do any good or is it a waste of time?