The event looks like it is a force push (also know as new revision) of an existing proposal so it isn't displayed by `ngit list`.
The reference to the original proposal is actually a reference to a kind 1 event and there isn't an original proposal therefore it doesn't get displayed.
The event was almost certainly created with `ngit send` with the `--in-reply-to` flag referencing the kind 1.
`ngit send` does no checks to ensure `--in-reply-to` is actually a root proposal. This caused the error. This is a bug that should be fixed.
The language 'in-reply-to' is super miss leading. It is used because it replicates the functionality of the `git send-email` 'in-reply-to'.
There is a potential feature request here also. `--in-reply-to` should support referencing other events: kind 1s, issues, or even other things.