Prey’s optional "Whistleblower" objective takes a while to pay off. You’ll pick it up when you’re exploring the psychotronics lab during "Detour," but you won’t be able to wrap it up until you complete "Shipping and Receiving." The last task, though, takes place in what amounts to a warehouse full of loot, so it’s worth the time, and it solidifies some of the background story of Prey, fleshing out the world a little more.
Annalise Gallegos’ office
When you explore Labs B and Annalise’s office in Psychotronics during "Detour," you’ll find a TranScribe next to her corpse. Listening to it will inform you of her doubts about the legality (and morality) of the experiments happening on Talos 1. The rest of the TranScribe has a conversation between her and someone named Quinten Purvis. The two of them have planned to take what they know to the media.
Search Dr. Gallegos’s habitation pod in crew quarters for evidence pertaining to what went on in Psychotronics
You have opportunity to explore the habitation pods at the end of crew cabins B during "Gathering Echoes." Annalise’s pod is in the middle row on the bottom left. Maliah Fowles’ corpse is there, along with another TranScribe. This one reveals that your brother Alex wanted Annalise watched.
Search the security station in crew quarters for Officer Fowles’s surveillance on Annalise Gallegos and known associates
The security station you’re looking for is, oddly, not actually in a security booth. The surveillance is on the concierge desk computer (under the utilities tab) in the main lobby of the crew quarters (which you’ll visit during "Gathering Echoes"). The recordings will point you to a cargo container in the cargo bay, but you’ll have to wait until completing "Shipping and Receiving" to get to it.
Search cargo bay for the secret crate where Quinten Purvis intended to hide
After the end of "Shipping and Receiving," you’ll open up cargo bay B and get access to the computer that unlocks any cargo container inside. (You can probably seek out the cargo bay before getting to this point in the main story, but it makes a lot more sense — and is a lot more convenient — if you come here after "Shipping and Receiving.")
Spend a few minutes wandering around and unlocking every container you can find — all you have to do is put the four-digit code into the computer and hit unlock. Cargo bay B is full of goodies.
In the back left corner (from the computer), there’s a door to another section of cargo bay B. There’s a container right in front of you — cargo container 3232. Use either the computer or hacking 2 to get it open, then pick up everything inside.
Collect Annalise’s thumb drive
One of the things you’ll pick up from Quentin’s corpse is Annalise’s thumb drive. On it, she details the hard-to-swallow truth about neuromods. Ironically, you’ll also loot a couple neuromods from his corpse.