@michael_dunn Welcome to the forum!
No, you wouldn’t get an email about a master password change.
But if someone else logged in to your account, you would have gotten a “New device logged in from…” email. Did you get such an email (for a time period, where it couldn’t have been you logging in)?
Follow the advice of @bwuser10000 of keeping the device where you are still logged in disconnected from the internet. Without your master password, you probably must export everything manually, one by one…
Here is a comprehensive list of things you could consider and try also: [Guide] "I can't login" - Some tips for login problems/issues
But to be blunt, if it turns out you really have lost your master password and there’s no way to get it back - and it’s not for other reasons you can’t login at the moment - then your account is lost now.