Fount this problem today and must share it with you.

01:09:18 root@eeny:~# zpool import tm
cannot import 'whatever': no such pool available

Oops, got scared a bit :)
You should not because what follows may help you.
That is assuming the disk with that pool is attached, available and not damaged :D

The pool was found on the disk:

01:09:56 root@eeny:~# zpool import -d /dev/sdc1
   pool: whatever
     id: 6969696969696969696969
  state: ONLINE
 action: The pool can be imported using its name or numeric identifier.
 config:

	whatever          ONLINE
	  sdc1      ONLINE

And now I mount it:

01:10:44 root@eeny:~# zpool import -d /dev/sdc1 whatever
01:12:37 root@eeny:~# df -h | grep /whatever
whatever                       3.4T  3.0T  429G  88% /whatever

DONE! :)