It's possible that the NYT never had "physical possession" of the memo, just what was read to them, orally delivered.
They could have an e-mail, digitally delivered. The mail could be an exact copy of Comey's memo with complete headers, or excepts. Comey's name could me "masked" from an email, so NYT would have to trust its source.
I wouldn't say the physical possibilities are endless. But no matter how you slice it, Comey leaked directly or indirectly to the NYT, before the May 12 tweet.
We can find agreement on this point. Comey leaked directly or indirectly to the NYT before the May 12 tweet. But there is no evidence that any memo was the basis of the May 11 NYT article. None. And if the NYT did not receive a memo (directly or indirectly) and instead relied on interviews for the May 11 article, then Comey may have been truthful when he said the memo leak was in response to President Trump's "tapes" tweet.