I think the most obvious answer is that alphaama is only using the damus relay and this event isn't published to the damus relay.

also cameri turned off mirroring yesterday because of the spam attack, so this happened -- which is good, because it forces us to think about the future in which there will necessarily be events that will only be in some relays and not others.

the most immediate measure should be that the replier's client, jb55 in this case, should append to the 'e' tag the address of one of the relays where the note he is replying to was found. then alphaama must use that to query that note.