Op what is the cause of the hack? Is it because you didn't use a solid password or what could be the issues over here. Most time people hacking your account are those closer to you that is why you must learn to have a complicated and mix password where it would be too for someone to memorize it except you.. you are really lucky to had have this immediate attention sometimes most of the hack account ends up taking loan on the forum without the real owner's knowledge when it's restored back you start paying loans you didn't know about.
Most of the time when they use public cyber and without logging out, it can result into third parties access to the account, I guess that is the case here since the hacker doesn't have access to the email it shows that the account access did not originate from his device, because if it could have been from his device, the hacker could have done an email change and taken total control of the account, but the case is not so since the ops was able to lock the account.
Having provided the sign message from an old wallet used on this forum, make the process easy and only time taking, but keep sending a reminders may be once in a month or two weeks interval.