I think there should be a setting on VLC 'Album art policy' or similar - make sure that is set to download 'as soon as track is added'. To be honest, I'm seeing less Album Art with the latest VLC but do still see plenty on the remote.
I see that message all the time and have never had any issues. Tempted to say it must be unrelated, were you doing anything else during the same session? - but if that's what you saw happen then it did.