after `rsvp move` a `ping` from new topic does not work

[brainwane]

In https://recurse.zulipchat.com/#narrow/stream/19393-oss-at-rc/topic/Oct.2012th.3A.20talk.20on.20joining.20an.20existing.20project I moved to a different topic and got confirmation it worked.

In the new topic I posted rsvp move and got private-messaged an error,

This thread is not an RSVPBot event! Type rsvp init event-url to make it into an event.

[brainwane]

But posting rsvp move from the old topic didn't work either; I got the same private message'd error.