I have a long commute in and out of a large city. Since I spend so much time on the road, I always try to get the details of Amber Alert notifications to be on the lookout for vehicles used in abductions. I guess I can't do that anymore since Twitter requires an account to see Amber Alerts. Hopefully my state finds another platform to post them.
Not sure about what carrier you use or what device you use, but I'm on AT&T using a Pixel 6a with CalyxOS, which is just de-googled Android, and on Android if you accidentally swipe away an amber alert notification you can find it again by going to:
Settings -> Safety & emergency -> Wireless emergency alerts -> Emergency alert history
But your point still stands, governments and public institutions really need to stop relying on privately owned and operated social media platforms for posting stuff like this. If they want to use a social platform to publish alerts, they would be much better off standing up their own Mastodon instance that is "just" for those alerts. People could follow those accounts if they want, and those institutions wouldn't be subject to the whims of overpaid unpredictable man children.
Good info, just wanted to add on with instructions for both major mobile platforms. Depending on your specific device and version, there may be some slight differences in how the menu options are worded and you might need to expand a collapsed section in the menu to see the settings.
Source: Google support