[nosoop]

Going to be that guy so I can put this question to rest. I had a similar issue back when I needed to detect the shove (for a custom achievement); I revisited it today after working on some other projects that had me thinking.

Use a hook on OnTakeDamage(Post|Alive|AlivePost). It does work (if not before, it does now):

public void OnTakeDamagePost(int victim, int attacker, int inflictor, float damage,
		int damagetype, int weapon, const float damageForce[3], const float damagePosition[3]) {
	if (attacker != victim) {
		// attacker is equal to victim on shortstop push events
		return;
	}

	if (!IsValidEntity(weapon) || !HasEntProp(weapon, Prop_Send, "m_iItemDefinitionIndex")) {
		// we don't have a weapon to work with
		return;
	}
	
	if (TF2_GetItemDefinitionIndex(weapon) != 220) {
		// not the shortstop (personal stock function, but you should be able to figure it out)
		return;
	}

	int owner = GetEntPropEnt(weapon, Prop_Send, "m_hOwnerEntity");
	LogMessage("%N bumped %N with shortstop", owner, victim);
}

A couple of other things that need tweaking:

• The player_hurt isn't fired in a way that the attacker can see. No damage numbers.
• Killing a player directly with an initial shove doesn't propagate the weapon through player_death (on a non-assist it acts like the player suicided). On multiple hits within a short timespan, it's treated as an assist.