Even when you don't see any other players in the zone, the wild pet population has been affected by the other wild pet hunters. That's one reason it can be tough to find those low level rares. So, here's a tip: keep looking on your mini-map for your wanted pet and when you have the icon, but can't find the pet, don't give up! The pet is likely hiding in a nearby object, like a tree. Everyone else in the CRZ gave up... that's why it's still waiting there for you!
First, go into Key Bindings from the Game Menu. Scroll down until you see "Interact With Target" on the left. Note the assigned key-- click on the red button if both of the ones in that row say "Not Bound". Pick a key combination you never use (Ctrl-K is good for me) and then hit OK.
So now, back to the no-see-em pet. Get as close to where the icon appears in your mini-map as possible. Use your keypad + key to zoom your mini-map view. Now type /tar PetName where PetName is the first few letters of the wild pet's name. You should see the pet is now appearing as your target, although you still can't see it. Now use your Key Bind-- Ctrl-K for me, and it should take you into battle with your invisible pet.
I have found numerous hard to find pets this way. I found 2 rares hiding in the trees this way just today. Note: after the first time, you won't need to set up the Key Bind again.