I tested it here a few times, logging in with a wrong password does not generate an email, while logging in with the correct password from a new IP does generate that "Someone just used your master password to try to log in to your account from a device or location we didn't recognize" email.
Could you try again logging in with a completely wrong password (to see if you get a email) and then logging in with the correct password from a new IP?
Also, you can verify that those kinds of events (wrong password and correct password from new IP) are logged in the LastPass Account History. Instructions to get the Account History are here https://news.ycombinator.com/item?id=29708122