In Ninja Burger, you can pick up various forms of training (such as Training Course: Combat), which give you a permanent +1 bonus to a skill (and can be used as an auto-success if played in response to failing a roll). They have one last line of text: If your current character is lost, discard this card.
How does this work with the card Extremely Clever Disguise, which lets you discard your character and pick a new one? (Because you've just been disguised as your old character until now.) You're not exactly "losing" your ninja, but you do discard the old character card.