I sent tells to him while he was still on but for some reason my client wasn't displaying the tells so I don't know if my client was bugged or what. A few seconds later he was no longer online and I didn't hear a word from him.
That's because he /q'ed out of the game, and if you send tells you an LD character, it won't display your tells to you. Pretty much screams "guilty" to me when you kill a mob, loot, and /q out of the game. Since time between afk and mob spawning is undetermined, the "loot n' scoot" action the player took is that of a person trying to get away with something rather than rectify it.
Vallby/Tallby and crew did this exact thing constantly when farming for CG/FG stuff, and they got away with it. Now they're farming T3. Crime does pay sometimes.