It's not clear to me what other records they would have in that case and again, this isn't exactly being "disappeared" given that they were turned over to the police for processing and then released without charges. Sounds more to me like some cops were lazy with the paperwork when they were going to release them anyhow.
The feds have wide-ranging authority to arrest people and always have, though:
https://www.lawfareblog.com/what-heck-are-federal-law-enforc...
If that happened to someone you were walking with and they left you there, wouldn't you call police and report that your friend was abducted?
Also, the government officials have claimed the people weren't arrested, and my understanding (which could easily be wrong) is being detained by law enforcement means you're not permitted to leave, not that you must go with them, so I'm out of words.
http://opb-imgserve-production.s3-website-us-west-2.amazonaw...
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It appears that the State has largely backed away from any argument that the federal agents were not at all identifiable as law enforcement. Mr. Pettibone acknowledges that their uniforms said “Police,” Pettibone Decl. [1-1] ¶ 3, and the video shows agents wearing clothing clearly marked as “Police.”
One article had an account of someone abducted, searched, and released, and then the authorities said they did not have records of arresting him. If there's no records, it's not the regular court system, even if it happened in the court building.