You’re both correct— tptacek is correct in that the 4th amendment is constrained to government search and seizure and there is no positive assertion regarding privacy written into the constitution. But you’re also correct in principle, as the strongest positive assertion regarding privacy (in general) from the U.S. federal gov’t originates in the Supreme Court’s decision in Griswold v. Connecticut from 1965, and Justice William O. Douglas’ reference to privacy as a right inferred primarily as ‘penumbras’ extending from the more specific guarantees of the first 5 amendments.

Edited to Add: All bets are off now, as the court has explicitly reversed stance on this as it regards abortion, which leaves a big precedent for expanding future privacy “exceptions”.