@danejbaker sorry to hear that! Cockerels along with all other items dropped on the ground disappear after server reset. Next time be sure to have a cage ready before you breed to avoid losing your cockerel. If the NPC does not have any cages for sale at the time then come back later.
Cockfighting Arenas are currently disabled, they should be enabled sometime soon though I do not have an exact date at this time.