"But of course," he responded, smiling. He wondered if Mrs. Lestrange might have been something of a task master. "I only meant—that is, you've secured the artifact and the vault appropriately?"

He doubted very much otherwise, but would not be doing his due diligence if he did not verify this with Miss Scamander.

WHAT DO YOU DO?
a. Lie. Well, stretch the truth—the vault is locked, and the artifact is secure...with you.
b. Admit the truth
c. Say you should double-check and return to the vault, hoping he does not choose to accompany you