A customer of ours that is an attorney was the victim of the unseen crack and he was gracious enough to be satisfied with a new frame. He advised us to turn down any frame inspections of this nature. Frames involved in wrecks, as he put it, puts "undue liability" upon the shop should we inspect them, making us directly liable for injury or harm if one fails. Be it aluminum, steel, titanium, or carbon, off to the manufacturer it goes for inspection.
For what it is worth, he did let us know that regardless of who inspects it, should someone decide to sue due to a wreck from a frame failure, the shop will most assuredly be involved in it.

As for the ugly responses in this thread, put all your assets on the line and do frame inspections for people. I'm sure they will appreciate it.