Secrets of the Key {U}
Instant
Investigate. If this spell was cast from a graveyard, investigate twice instead. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Flashback {3}{U}
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
Kellan, Inquisitive Prodigy // Tail the Suspect 99%
$0.32#4405
"Investigate. You may play an additional land this turn."
Eliminate the Impossible 89%
$0.08#22411
"Investigate. Creatures your opponents control get -2/-0 until end of turn. If any of them are suspected, they're no longer suspected."