It's so easy to cast suspicion especially with bias for whatever reason against anyone. Solid proof on the other hand is a different matter.

They had access to copy machine records. They could have suppoenaed all phone and text records too

Can’t do that unless it’s targeted, you can’t subpoena all the people with access for their phone records and texts (they obviously wouldn’t have used a work phone) personal phones would a no no without probable cause, against one specific individual.

The Supreme Court can do pretty much anything they want to within the law and they could have. I heard some legal analysts discussing it today  and they said it was decided privately not to pursue it further.

No they can't, they cannot unilaterally override a person's right to privacy without due process, part of that process is having evidence to search someone's phone, broad suspicion of a number of individuals who had key access is called circumstantial evidence, the Supreme Court literally exists to protect the rights of everyone, including whistleblowers, what you're advocating for is a revenge fantasy based on your political ideology, that's what you get with a dictatorship, is America a dictatorship? 

Until you can pin down one specific individual with enough evidence to invoke probable cause to conduct a forensic search of electronic devices, you aren't going to find the person responsible, only a strong suspicion of who it might be, would you like to be accused and convicted of a crime you didn't commit because you, along with several others "fit"? Probably not, you'd want your rights protected.

I voted other.

With current DOJ and FBI, do you really think they're looking for the actual leaker?

FWIW

The problem is it will happen again. An assassination attempt on a justice happened after that so it had reprocussions.  They need to pass a laws making a leak like that a felony.  The most likely scenario is that someone took the papers home, let a spouse or friend or someone see them and that person leaked them.  With enough pressure, those who had access could have been encouraged to cave and admit their culpability. If nothing else, everyone should be removed from those jobs since now they can’t trust any of the clerks. It’s very unlikely a justice did it as they have too much to lose.

More information 

The clerks all left in July so going after them was nearly impossible.  

Neither side really wanted to admit the possibility of corruption within the court.

Politico never would have published unless they were 100% certain it was the real decision, so someone there also knows the identity of the leaker. They will never reveal it intentionally.