Yeah. The sword throw indeed is buggy.
First, if you have already thrown your sword away, when kicking-parrying the enemy's attack, the sword will still be shown on your hand. However, the execution parry can not be carried out.
If the sword dance was executed a lot of times in a crowd of people, when it struck someone, it would disappear, and you'd no longer be able to get it back again. However, if you kick-parry, the sword will still appear in your hand... and somehow the execution can still be activated? So it's either in a state where the system thinks that you still have the sword, but you can't use it except for parrying... or that the system thinks that the sword is thrown; however, that conflicts because there is no sword on the field, so you can't use your sword except for this way?
Too confusing, really.