While washing my car today I noticed that underneath the hood next to the A pillar on the passenger’s side there’s a missing plastic piece. Anyone know the purpose this piece? I had the vehicle serviced back in December so could the dealership forgot to put it back on then and I didn’t notice since there was no car washes in the winter?

 

The piece looks to be an isolator of some sort that acts to separate the under-hood area from the door area. At first glance, I thought it was simply a finishing piece. But, after taking a peek at my car and seeing the "blocking" nature of the piece, it looks more functional (e.g., sealing off an area of the door's wiring loom from contaminants or possibly even engine sound) than cosmetic. Just a guess though.

 

Maybe your car was produced on a Friday and the employees were in a hurry to leave for the weekend.

 

That would be my guess as well. It will keep the airflow going in the right direction.