MacOS – How to get the password hint for an encrypted disk

I created an encrypted disk on a USB drive the other day, and added a password hint. I don't remember what the password is. (I have a scheme for mapping hints to passwords, so when there's a hint available I just pick something random and write out the appropriate hint.)

When reconnecting the disk today, OS X popped up the password prompt – but no hint displayed.

When I go into Disk Utility and try to mount the volume, same thing. Not even a button to show the hint!

So now I've got no idea what the password is. How do I find out the hint?

OS X 10.12.6 (16G29)

Here's the process I went through. (I went through it again using a spare SD card and took screen grabs at each point.)

1. From Disk Utility, select disk in question and go to the Erase option. Select Mac OS Extended (Journaled, Encrypted)

2. The password box appears. Enter password and add a hint.

(I usually pick a more cryptic hint than that)

3. Click Choose, then click Erase, and it will do its thing. Click Done once it's done, and quit Disk Utility.

4. Eject the newly-mounted encrypted disk image from Finder, then unplug USB hard drive.

5. Reinsert USB hard drive and wait for password dialog to appear.

But where's the hint?!