If you have access to the truck, you can take a look at the fracture surface of the shaft. If there was a crack there before your accident, you will see different wear marks between that existing fracture surface and the final fracture surface. The existing fracture surface (area where the crack was) will have wear marks that look like a bunch of "C"s and it will be relatively smooth. The final fracture (at the time of the accident) will have a different surface, it will be rough and jagged. I worked for a few years in a metallurgical lab with this stuff, it was an interesting job.
2004 Ford Ranger Edge manual 4.0 4x4 with 3" Body lift, 33x12.5 BFG A/T KO's, on Eagle Alloy 057 rims, and alot of mods
2011 Ford Mustang GT 5.0 manual with no mods yet
2005 Ford F250 automatic 5.4 4x4 with no mods