jm MN!@CgÉ(Ì©zkÂNû!-<½ò¹à` L®If the parent key was never used for memo, and the memo.cash website itself generated child keys, then at configurable threshold sent to parent keys, you could minimize risk.
https://whatsonchain.com/tx/d65eaecbdb14165d9eab650936d467ea90d760be848e4f9351ec75c41e273f91