Other unmount USB drive: Device not configured

Hi all,

When I accidentally move the cable, the mounted drive is disconnected for an instant. And ls gives:
% ls mymountpoint
ls: mymountpoint: Device not configured
So I unplug the device, and try to unmount it:
# umount -f mymountpoint
umount: mymountpoint: statfs: Device not configured
umount: mymountpoint: unknown file system
# umount -f /dev/da0p1           # This seems to work
But I still have this:
% ls mymountpoint
ls: mymountpoint: Device not configured
Indeed, the system still "thinks" there is a device mounted on this directory:
% mount
/dev/ada0p2 on / (ufs, local, journaled soft-updates)
devfs on /dev (devfs, local, multilabel)
/dev/da0p1 on /usr/home/me/mymountpoint (ufs, local, journaled soft-updates)
The device is likewise listed in the output of df -h.

The mount manpage states that "the system maintains a list of currently mounted file systems". So the question is: How to update this list?

This may be a very common problem, but I struggle with it for years. This is not the first post on this problem, but it has never be solved, as far as I know. I think the solution is very simple.

Workarounds: reboot the system, or mount on another directory.

Any advice is welcome.