Tomas from the collector's quest (as opposed to "Thomas", but I guess this is what was meant) is supposed to be in a certain Trinsic shop.
Rumour has it the invasions made him take up roots and he now wanders around the town.
Elwood is the character found in New Haven.
Ah, ok; thank you.
-Galen's player
Do note that he could and DID chase people out of town, while in "Hatred" mode. There were some training exploits one could use with him once the town was back to normal, and he was outside the guard zone, so the people using those exploits have hardly been paging to have him put back.
The range of the zone affected by the invasions goes to the Hidden Valley to the West, North to the Spirituality shrine and the Swamp, and south to the jungle below the river. So, he could have wandered to any of those areas before hitting the boundary and reverting to normal. In addition, while still yellow, he attacks aggro mobs, so can and will chase them (meaning mongbats and Ogres in the area will cause him to wander further).
On the other hand, if you do find him outside town, if you can get an ogre to chase you, and Tomas to chase the ogre, you can get him to follow you back into town at least.... Granted, it might take a few ogres (Tomas has leet wrestling skills and will kill an ogre rather fast, if it stops to fight him)