iCloud password reset locked me out of macbook

I have a new macbook pro 13 with OS X 10.10.5. Its setup to use my iCloud password for login. I set it up and then immediately went out of town for a few weeks and forgot the password when I came back. I received the login screen message "This account uses an iCloud password......" which instructed me to use another device and reset my iCloud password at appleid.apple.com. I did. Macbook still wouldn't let me login. I resolved the problem by booting into recovery mode and using the resetPassword utility. Luckily I hadn't put anything important on it.

I need to resolve this issue from potentially happening again. I would like to secure my device a little better, turn on FileVault encryption, use a firmware password, etc. I don't intend to forget my password again but I DO regularly change my password. I don;t want this to lock me out again and cause me to lose data. What happened? If using iCloud passwords as a login is not reliable why is it an option?

Also, if I can reset my iCloud password online to unlock my macbook this would imply that my macbook can get online. I had previously connected it to my wifi so it could possibly have gotten online to retrieve the new password. However, it is my understanding that my WIFI password is stored in my keychain, which is secured/encrypted with my OLD password. How could this ever work for any macbook? If it can't unlock the keychain with the old/forgotten password to get the wifi password to get online and retrieve/check the new iCloud password? Just a thought.