Rattle Noise at Low RPM's

I took my 2011Prius into the dealership today and tried to get them to fix the rattle noise.
Fender Rattle/Tick Noise (T-SB-0064-12)
The rattle noise is louder after a cold start and then gets quieter.

The mechanic drove first and put too much gas to trigger the sound.
I took over afterwards after the car had warmed up and the sound was smaller but he claimed he couldn't hear it.
He said to wait until it gets louder and bring it back to fix.
Felt like he just wanted me to go away.

Next time, I'm going to park on the street the night before and make them come to my car and I'll drive first.
I feel like this will take many visits to fix.
I wonder if I should just follow the other people and start stuffing towels to reduce rattles.

I love my Prius but this is just disappointing.

 

About two months ago, I bought a 2010 Gen. 3. I have noticed that there is a rattling sound when I am driving at low speed. Will be taking it the the dealer and see what or where the rattling noise is coming from. I love my Prius too but it is disappointing to me too. If they find the cause, I will get back to you.