I use to have a GM 12-bolt. When I was still in college I drove all the way to Chicago to get it. I say 'use to'. Came home one day and somebody had taken it. I HATE a thief. My guess is they took it to use (not scrap) as they left the 7.9" S-10 axle that was sitting next to it. I hate to think some a-hole is out there driving around with my 12-bolt under their car.
Also had someone rip the Sun Tune II tach out of my Nova. They didn't even cut the wires, they grabbed and pulled and broke the fill panel that goes under the steering column. Grr that makes me angry.
Sorry someone dragged off your engine. If it just happened, you might stop by a few of the local recycling yards. You might see it sitting right there in the pile.