When the player (left sprite) is moved into the right sprite, using the right-arrow key, do you want the player to be teleported back to its original position?
If that's the problem, the reason it's not working is that the "body_entered" signal isn't connected. To fix that, you can connect the signal in the _ready() method in Spike.gd:
func _ready():
player = get_node("/root/Node2D/Boho/KinematicBody2D")
# warning-ignore:return_value_discarded
connect("body_entered", self, "_on_Spike_body_entered")
You can also connect a signal using the Inspector, but it's easier to explain how to do it with code.