The one who wanted to be bought retracted that wish after hearing they were there for Jack. I think it is him still since the sadist wouldn’t have a reason for doing so and the other one was too busy getting beat up.

Plus the name carving sounded like demented way to thank Shepard for their escape.

True. But i told the guard to stop beating the dude up.

That mess was all on greedy Warden Kuril. Had he simply completed the deal, and sent Shepard on the way with Jack, the rest of the prison-ship would have remained intact. Billy was just some random crazy-person who lucked into Shepard's email. The ex-prisoner heard Shepard was aboard and fixated on the Commander to 'make a name'. As stated, had Shepard actually shot at 'Billy', the dirt-bag would be dead.

I checked the files and it was prisoner 24601 LoL

Oh, so that wraps that up.

Title: (Untitled) From: (Error, Invalid Sender Name)

Hey Shepherd [sic] heard I have you to thank for getting out of Purgatory (sent a ship to round me up, but they didn't weapons-check good enough)! I'm gonna carve your name instead of mine into my next victim as thanks, got anyone you need dead (haha)? You did take a shot at me though on my way out so I have to kill you, you know how it goes. Dad taught me that you let anybody hurt you, they get ideas so you make sure to send a message, not like I'm sending now, though! See you around, the people who live here are coming back and it's showtime! Look around for your name, I'll make sure you find it before I find you! Billy...

Not a friendly email, but that's what it says.

I believe the team who worked on ME2 wanted to include that storyline but didn't finish it in time for the release because they were all more focused on the storylines for the main characters and the main mission. While there are other missions but they all feel more like filler missions to raise experience and resource points because bioware wanted to keep their focus on the Normandy crew and whoever associated with shepherd so in short there were several mission ideas but not all of them were realized and were left unfinished by the time of game release

If this git is blue suns of eclipse. Odds are they aren't around anymore. Shepard goes through mercs like their tissue paper.