Heatshield removed during mot.

Hello,

Having just had a health check on my toyota auris 12 reg. I have been told it needs a new heat shield because its an mot failure not having one..

Now my query here is that my local garage removed my heat shield instead of reattaching it during its mot. As it was rattling... As they never offered to reattach or even give me it back, I assumed it wasn't needed...

But how could they pass the MOT and remove my heatshield of its an MOT failure??

Thank you

Danielle