Pet Display Issue

Platform, device version and operating system:
PC, Windows 7

Screenshot or image:

What you were expecting to happen, and what actually happened:
Right now my collection summary shows me as having 71/69 pets, even though I’m missing several from the underworld. If I list unowned pets, I only see Lil Freedom.

How often does this happen? When did it begin happening?
I noticed this tonight.

Steps to make it happen again