umount: /home/diret/mount: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))

I tried everything (fusermount -u) to unmount it but the only thing that worked was actually doing this:

ps aux|grep sshfs

Then I identified the sshfs connection and did:

kill -kill pid

After that it was obviously unmounted.  I think it happened because the target SSH host crashed at some point.