how do i get my friend account back

hi the account that was hacked is called cyborgmeister and i just saw him play. we tested everything and nothing worked. he dint link his email becuse he could not do it for some reasons. i dont know what to do in this senario and this has happend for somtimes. if u have any advise on how to get it back plz let me know ps the hakker changed password and email.