But it is very easy to imagine a service that scrapes sites with canaries and publishes an affirmative list of those which took theirs down recently (or in a given time interval).
Reddit released its transparency report for 2015 and the warrant canary language was missing.
Maybe that's an edit after your post. I agree that a silhouette of an expired canary lying on its back, wings spread awkwardly, tongue sticking out, eyes crossed, would make this communication more effective.
Yeah, that's odd. It's timestamped March 31st - perhaps it was serving a stale application level cache (I've not been to the site in a while, or so I thought). Now the canary-logo is taken down from the reddit listing on the front-page too.
https://canarywatch.org/