What's Nostr kind=892? Is this a public message, or encrypted DM?
The way I see it: Nostr data is forever. Like nude pics on the internet.
Yes, there is is NIP-9 Delete request events, but each relay operator is in full control of his database and you have to trust that they actually obey the Delete request, and not keep logs or backups.
Would be better for the whole mix/coordination to be truly ephemeral imho..