FreeBSD 11.0 boot pool created by installer -- how to import and mount using installer?

[David Christensen]

freebsd-questions:

I have a FreeBSD 11.0 RELEASE i386 system that I created using the 
FreeBSD installer (FreeBSD-11.0-RELEASE-i386-memstick.img):

         Partitioning                    Auto (ZFS)

         ZFS Configuration
             Pool Type/Disks             Stripe 1 Disk
                 Virtual Device type     stripe
                 (device)                ada0
             Pool Name                   zroot
             Force 4K Sectors            YES
             Encrypt Disks               YES
             Partition Scheme            MBR (BIOS)
             Swap Size                   2g
             Mirror Swap                 NO
             Encrypt Swap                YES
             Install                     Proceed with Installation


I broke the system by attempting to change the root pool passphrase.  I 
might be able to fix it if I can edit /boot/loader.conf.


Booting the FreeBSD installer into multi-user mode and then going to a 
shell:

# zpool list
no pools available

# zpool import
     pool: bootpool
       id: <redacted>
    state: ONLINE
   action: The pool can be imported using its name or numeric identifier.
   config:

          bootpool    ONLINE
            ada0s1a   ONLINE

# zpool import bootpool
cannot import 'bootpool': pool may be in use from other system
use '-f' to import anyway

# zpool import -f bootpool
cannot mount '/bootpool': failed to created mountpoint


Choosing Live CD produces the same end result.


I previously obtained the same end result by booting into single-user mode.


How do I import and mount bootpool using the installer that created it?


David