I doubt that buck had any idea that another deer was shot at the same spot. I really don't think a deer has any ability to reason about getting pissed off b/c another deer was shot. There doesn't have to be a rub line in order for there to be a rub, especially if you have a lot of young deer in the area. Just my opinion, I just think some people give deer too much credit for being able to think and reason about certain situations, they just go off their senses and natural instincts. And b/c their senses and natural instincts are so acute, that sometimes leads you to believe they are smarter than we are.