There is a method on the database that allow to check where an event ID was seen:

```rust

let database = client.database();

let relays = database.event_seen_on_relays(id).await?;

```

This works with the in-memory database (which is used by default) and with some persistent database but not with all implementations (like with nostrdb).

Another good solution is to use the `RelayPoolNotification`, like suggested by nostr:nprofile1qqswgvmv65ja7706f5a0xe8ajcqdfvgdeeppt2jvx0kh06sggg6ykyqppemhxue69uhkummn9ekx7mp0qys8wumn8ghj7mn0wd68ytn9d9h82mny0fmkzmn6d9njuumsv93k2tcpr4mhxue69uhkummnw3ezucnfw33k76twv4ezuum0vd5kzmp0v9ru2a