Well, the reason I don’t view it as a euphemism is because it’s typically associated with totalitarian regimes. The government “disappears” people. See here,

to cause (someone or something) to disappear:

a: to abduct and kill or imprison (someone, such as a political dissident) while withholding information about the person’s fate

Her son was disappeared during Argentina’s so-called ‘Dirty War.’— Associated Press

“Disappearing” someone carries more weight than “abducting” someone.