I agree to a point.  The packer took advantage of the situation, but the cattle feeding industry put themselves in the predicament.  Any and every time the feedlots are not current it puts the packer in control and he will bid as little has he can to get cattle bought when the feedlots have to move them because they are too big or because the yards are overstocked with feeders coming in.  It happens every time, and anyone with a little grey in their hair should have seen it coming.  The fact that prices rebound only means that they need more cattle somehow - they are not going to drive the price up to make a better profit, because that cuts into their profits.
Remember that the packers are not a service organization for the feeding industry . . . they are customers of the feeding industry.  And just like farmers will shop for the best deal on seed, fertilizer, fuel and feed, the packer is not going to pay anymore than they have to to buy cattle.