The Case of the Mystery Suitcase Placement has been solved.
When I arrived home from work on Thursday evening all cars were away. It wasn't until I saw the suitcase without the car sitting next to it, that I realized, maybe they were just trying to get rid of the suitcase and just had it placed in such a way that it looked like they might want to pack it into the trunk of their own car.
Friday morning, our trash day, they had the suitcase positioned differently right next to a stroller they had left in the yard for 3 days, making it more obvious of their giveaway intentions.
I don't know if anyone ever claimed it or the trash man took it. Either way, no more suitcase.