Take something flexible like a like a long thin spring.
Wrap about an inch wide strip of duct tape around the bottom 1/2 inch. put a vertical slice in the 1/2 inch of tape below the spring and fold it back over it's self so the sticky side is out.
Slowly fish around with that. The plastic piece will stick to the surface and you can get it to the hole where you can see it and grab it with something.
