In regards to the spike sticking on ATC:NG, it would have to be driven in significantly past the point where it is widest, and the material would have to be capable of binding back around the spike, thus it would have to be elastic in nature and quite strong. The material would also have to be hard enough to be able to resist being cut by the sharpened edges as otherwise it would just cut its way out when you jerked on it.
For example, it would not stick in wood, because the wood would split out from the wedge and the crack would not reform around it. Nor would it stick in flesh, to any degree, because while it is possible for it to catch, just imagine stabbing on a downward arc, when you went to jerk the spike out, it would easily cut out through the flesh, generating one hell of a wound.
A couple of things do come to mind. If you stabbed it through a metal plate, using a downward arc, and then tried to jerk it directly out, the spike would catch on the metal. To get it out you would have to jerk it up and out, along the same path that it went it. Assuming this was on an individual, this might be a bit difficult, as they would have a strong tendancy to not remain upright after the initial contact.
You could test this by putting body armor around a sandbag or similar, and seeing how difficult it was to jerk the spike out, assuming of course you can drive the spike deep enough in the first place. I could imagine the hawk being ripped out of your hand if the individual collapsed. Put the rig on a stool, using say a 150 lbs sandbag, and then when you hit it, have someone kick the stool over and see what happens.
The other consideration would be heavy bone. Again, after stabbing on a downwards motion through bone, or across it, you would not easily be able to draw the spike directly out, the sharp edges would dig in and possible hand up on the bone. You would have again to draw it up and out along the path that it came it. I have not stabbed a lot of bone, but it does seem possible. You could test this on various animal skulls and large sections of meat, around ribs and such.
-Cliff