Where's the coolant fill cap on a v6 2011 camaro? Under the engine cover?

What is your question?

Looking for the radiator cap or coolant fill cap on the 2011 camaro, it's not apparent looking around the engine compartment. Didn't see it on the radiator where it normally would be found. Is it hidden under the engine cover? I saw something that mentioned that's where they hid it; is that correct? Developed a leak at the rear near the heater pipes that the heater core lines connect to, and I wanted to apply pressure with a cooling system pressure tester, but didn't see the cap.

What makes this problem better or worse?

Leak when hot and under pressure, overheat message