I only have the one Sonos alarm saved for use in our Main Bedroom, but that remains saved/works okay. In fact I just removed and re-added it, just to see and it’s still there after closing/reopening the App (Im using iOS controller FWIW) and it does not disappear.
If your issue persists after perhaps resetting the Sonos App and rebooting the local router, then it perhaps maybe best to reproduce the issue(s) seen and immediately submit a Sonos system diagnostic report from within the Sonos App, note it’s reference and contact/chat with Sonos Support Staff via this LINK and see what the Staff can perhaps suggest to help you to resolve the matter.