Answering more questions....
The bag type: white paper bag like a medium size McDonald's bag, but NO writing on the bag. ALWAYS the same type of bag. The ENTIRE bag goes in the window.
Window description: Goes to the only level of the house. There is no basement, no second floor. There are three windows on the front of the house. It goes in the window furthest from the door.
Drop off: the passenger gets out, does the drop off, gets back in car. driver pulls car into driveway. driver and passenger enter house together through the door. The car never is parked in the garage. I have seen that garage door open and trust me you couldn't fit a peanut in that thing.
Description of residents: mother, father, 2 sons (early 20's)
Pets: They have a dog. It's a pit bull, but it's outside regularly on a leash and doesn't seem too be too crazy. It will bark if I'm outside, but they tell it to be quiet and it does. So I don't think it's the dog they are throwing stuff for. The dog seems cooperative and follows their directions.
It's just too weird. I have my camera out so I can snap a photo if the drop off takes place tonight. I was gone this morning to the doctor and hospital for a terrific blood draw of 9 tubes,

so hopefully I didn't miss it today.