Other users already answered the questions you asked. I will just add a bit more information.

A normal use of a popular wallet wouldn't result in the generation of an address beyond the gap limit. I am not aware of any bugs that would cause this, but I can't rule out the existence of such bugs. It's more likely that a user customized its wallet settings to generate such an address, and that's not something you need to do.

About the passphrases.
Anything can be a passphrase. Your forum username 'markrockny' could be a passphrase. 'Markrockny' is a different passphrase that would generate a completely new set of addresses. It's essential you write down the phrase correctly including any spaces, numbers, special characters, capital/small letters, etc. By changing one character, you will recover a different wallet, and the software isn't going to tell you that it's wrong because there is no wrong passphrase. All strings (up to a certain length) are valid passphrases. Also, there is no wallet that can inform you that your seed has an extra passphrase attached to it. You must remember if you used one.