We consider https://images.linuxcontainers.org:8443 to be legacy. LXD these days uses simplestreams with most of its public image servers as that’s a lot less hackish than having to pretend to implement a rest api on a static web server 
https://images.linuxcontainers.org/streams/v1/images.json
This contains everything we expose. If you look for your fingerprint in there, you should find the matching record.