Formula for Docker 1.6.2 is not included in brew's index.
$ brew search docker
boot2docker docker docker-compose docker-machine docker-swarm
homebrew/completions/boot2docker-completion homebrew/versions/docker150
homebrew/completions/docker-completion Caskroom/cask/boot2docker-status
homebrew/versions/boot2docker133 Caskroom/cask/boot2docker
homebrew/versions/boot2docker141 Caskroom/cask/docker-compose
homebrew/versions/docker133 Caskroom/cask/docker-machine