If someone gets your phone, then can figure out how to log into your phone, Blink F-ing up and not having a secondary password is going to be the least of your problems. This is not a HUGE OVERSIGHT on incompetent Blink engineers.
If someone gets into your phone you will have banking problems, social media problems, identity theft problem, credit card problems, and on and on. Blink will be the least of your problems.
The real problem is YOU. You the lazy person that never logs out of your mobile apps that are on your phone. Its you, me and everybody else. Every one of those apps that are account based have a password for that app. That password IS your secondary password for your phone. Log out of those mobile apps when you are done. That way if someone gets into your phone, they have less of a chance of messing up your life.
Problem is, we as humans are lazy and trust that damn mobile phone too much.