Reasonable is a subjective word. The U.S. Constitution does not have any provisions for subjective terms. The only place where one can find where the Founding Fathers thought "reasonable" might fit is in the 10th Amendment which granted the sovereign STATES the right to determine what those instances might be. "Reasonable" is not granted to the federal government.
The Patriot Act cannot pass a strict constitutional test. It was passed AFTER the name was changed (formerly the Anti-Terrorism Act) when patriots were outraged. So it was given a gimmicky acronyn ("PATRIOT") for a name and passed. After all, since 9-11, who wouldn't be for a bill with the name PATRIOT in it?
The Fourth Amendment prohibits "unreasonable" searches and seizures. The Fifth Amendment requires "due process of law," which raises the subjective question of what process is "due." The Eighth Amendment prohibits "excessive bail" and "excessive fines." The Constitution is full of subjective words, which is one thing that keeps lawyers in business.