Okay, I looked (again) at the inventory screen. It shows I have no inventory. It doesn't show my cat.
Question: does going to the adoption center and picking a cat (which was free) do it? Or do you have to click on the "create a pet" link in the inventory screen? I looked at the "create a pet" link, and it looks like you can get a dog or whatever, without having to pay the adoption fee.
Umm... if your inventory screen is showing no cat under your inventory (and you had reviously created one), then, umm.. it's dead.
You'll have to go into create a pet and create a new one. You can go to the adoption center and create a new one, but that costs money. creating is free.