I don’t know if the dropped chain came first or not but the end result was the same a total failure of the rear dérailleur attachment arm. It appears that the force of the chain running forward, I was standing on an extreme up hill in the smallest ring of a triple crank pulled the whole assembly out and up and over ripping the skewer out and jamming the dérailleur into the spokes in the upper half of the wheel. After getting the bike home I pulled the mess apart and it appears the total damage is a bent skewer, an easy replacement. The roller cage is bent a bit and one of the two rollers is cracked, these are plastic and again should be cheap fix. But the big one and what I wonder if it can be fixed at all is the arm that attaches the dérailleur is bent at an very ugly angle. This arm appears to be cast aluminum and I don’t think it can be realigned? I’m sure that if I bend it back it will crack but can it be replaced or is there a place to send the whole thing out to be rebuilt? Would fixing this be cheaper than buying a new one? I can always ride my old bike while this one’s in the shop it needs a good going over, a yearly checkup and I could have that new crank I bought 8 months ago installed.