> He consented to the search of the laptop before being detained. He did not know it was an undercover police officer conducting the search, but that is not relevant.
I'm not sure you know what "consent" actually means.
https://en.wikipedia.org/wiki/Consent_search
A consent search requires the individual whose person or property is being searched to freely and voluntarily waive his or her Fourth Amendment rights, granting the officer permission to perform the search. Where consent is obtained through "deception" on the part of government personnel, the search may be determined to be an unreasonable search in violation of the Fourth Amendment.
He consented to a stranger searching his laptop, and the Fourth Amendment provides no protections against that.
He consented to the search of the laptop before being detained. He did not know it was an undercover police officer conducting the search, but that is not relevant.
He was subsequently detained, until such time as it became obvious he was innocent, and then released.