know the moment your site goes down
Paste your site's link. Pingbuddy checks it every 5 minutes and messages you on Telegram and email, with a screenshot, the moment it goes down.
Pace needs two or more snapshots. This launch has 1, so velocity and momentum read as unmeasured rather than zero.
A source that found nothing is a measurement. A source that has not run is a gap. Neither means the launch lacks the thing.