My goal is to make the throwingknife able to be picked and placed into the inventory of the player.

Your code is making the pickup trigger spawn only after the throwingknife has been thrown back (as it is a frag grenade weapontype the press g to throw back text spawns), sorry if my paragraph was hard to understand.

I'm trying to say that the pickup trigger will only spawn once the throwingknife has been idle and is being thrown back.
I'm trying to make the pickup trigger spawn once it has been idle in the first place.