If some unwitting 3rd party was hacked and used in a crime, you can't just go over to their house or business and "seize" their property.

When the criminals on cops run through your back yard, do the cops turn the inside of your house into a crime zone? Obviously, no. Even if the bad guy runs inside your garage, they are not confiscating your car, lawn mower, etc.

Contrary to popular belief on HN here, police / FBI don't just seize everything whenever they want. It requires warrants and probable cause. Good luck getting a judge to sign a warrant to seize a victims computer...not going to happen.