The Ars article seems to suggest that they were able to crack his phones pretty easily

Android uses data at rest encryption, which isn't really useful without a lockscreen PIN/password since data gets decrypted after you unlock your screen the first time after each boot

Although it doesn't appear he was actually using any encryption apps to store material; rather, he used a fake calculator app as password protection. Obviously not the brightest bulb in the drawer.

Agreed, he probably felt safe enough "hiding" the files. Definitely not the sharpest tool in the shed, which is great because fuck this guy