My Vagrantfile was deleted before the VM was terminated. The .vagrant folder was still there.
#### $ vagrant -v
Vagrant 1.6.2
I ran vagrant global-status to find the VM:
#### $ vagrant global-status
id name provider state directory
---------------------------------------------------------------------------
4ad5ef1 default vmware_fusion running /path/to/dir
Tried to force destroy the instance:
#### $ vagrant destroy -f 4ad5ef1
A Vagrant environment or target machine is required to run this
command. Run `vagrant init` to create a new Vagrant environment. Or,
get an ID of a target machine from `vagrant global-status` to run
this command on. A final option is to change to a directory with a
Vagrantfile and to try again.
Tried to destroy the instance without -f flag:
#### $ vagrant destroy 4ad5ef1
default: Are you sure you want to destroy the 'default' VM? [y/N] y
There are errors in the configuration of this machine. Please fix
the following errors and try again:
vm:
* A box must be specified.
To resolve: I manually stopped and deleted the VM in Vmware Fusion, and deleted the .vagrant folder.