There are several un-named letters found in FROST.
Inside a Desk inside the FMS Columbia Edit
"Esteemed Dr. Lerna,
This not what I signed up for. This ship has carried chems, weapons, secret corporate documents, and more than one exotic pet. But human trafficking? That is some deep shit. So here's the deal. The Liberty drop point is off. It just so happenes I nicked a certain little key off your dear associate so we're coming to your turf. I know about the tunnel too.
I want you to know that we are going to be having a serious discussion in regards to my compensation, or I let HR-D4 fucking walk.
Yours, Most Humbly,