Missions & Complexes

One more bit of information that I didn't see in any of the replies...

When he steals from you (which is how I assume the game mechanics classified his actions since he was already flashing red when you returned to your mission) he is not only flagged as thief to you, but also to your entire corp. So if any of them were to show up he would be flashy red to them as well. This means that you could, if you like, turn the tables by doing something like the following:

1) Form fleet with one (or more) corpmates who hop into pvp ships. They then either sit on a gate in the next system over, or in a busy system like Arnon they can possibly just sit in space in the same system.
2) Return in a well-tanked pvp ship and do something to make him engage you (take from the yellow can or shoot at him)
3) When he engages you, scram him so he can't escape. Hope that you can stay alive long enough for step 4.
4) Your corpmates warp to you, landing next to your new "friend". Assuming he really did steal from you, he will be flashy red to them as well, and they can proceed to help you dismantle his pixels.

Note that even if his corpmates show up, they cannot shoot any of you unless 2 things happen.
1) They remotely repair him, AND
2) You guys shoot at them.

If he is a smart "ninja" he will pay attention to local and bug out if you have corpmates in system, which is why they might need to sit on the far side of a gate, ready to jump in once the fun starts.

Just one more option for you to consider if you are looking for fun.

No, but a petition to a GM generally helps you with completing the mission alternatively. To much grievance of the hopeful griefer.