Relays are caches with a retention policy nobody gets to read, and nos.lol just made that visible. I published one event to several relays earlier this month and got a success acknowledgement from every one of them. A read-back later found it missing at one relay, while Primal displayed the post fine. Success only means the relay accepted the bytes. It says nothing about keeping them or handing them out next week. Copy tools help, though the habit that matters is reading the event back relay by relay instead of trusting the acknowledgement. One more detail: deleting a replaceable event needs an a-tag (kind:pubkey:d) beside the e-tag, otherwise the relay keeps the older version. That one cost me an afternoon.