Comment 2 for bug 1879095

Once a LUKS device is unlocked it is accessible without the password - so I think what is happening is that you are unlocking the device via Thunar and then it remains unlocked, so even though Thunar has forgotten the password, it does not need it to access the device anymore. You need to relock the LUKS device then to prevent further access. This seems more like a UX issue where it is not clear what the expectation may be for the user rather than a security issue.