Hmm I'm sure Alby has an explainer somewhere on how NWC works, but here's mine:

1. Basically, Alby runs a nostr relay - a server with a public ip and a generic API for sending and receiving messages.
2. When your Hub creates an NWC string, they generate a private key and associate it with the permissions to your lightning node that you specify.
3. Your NWC string gives SN, or anyone you give the NWC string to, this private key.
4. Hub listens for encrypted notes sent to Alby's relay where this public/private key is the recipient.
5. If SN wants an invoice from you, it sends a message signed/encrypted with this private key to alby's relay, then listens for the result.
6. Your hub, listening, sees the message, and checks if the bearer of that private key has permission to do the requested action.
7. If it does, Hub performs the requested action, encrypts the result, then sends it to Alby's relay.
8. SN, listening, now has the invoice it requested.

That shouldn't happen unless restarting somehow changed something on an Alby server somewhere, right?

Restarting more likely changed something on your computer, but it shouldn't have absent a bug or some reason only alby would know. I can't make sense of it.