It depends on how they delete it. There's no real delete on nostr. You can send a new request and ask to be forgotten by the ecosystem but it's just a request.

The old data lives on as long as it's on some relays and clients but if relays respect the wish and delete the events from their databases then the notes can be gone.

Kind of like emails. Once you send them out you're not in control of them anymore but can ask nicely to delete the copies.