Why do I see only 50 volts on my live wires?
I do agree with jsotola , inductive coupling created a voltage on this wire.  When next to a live line for a distance. Lines of force from the hot AC line induce a voltage if the lines ran further together the voltage would be higher (this is how transformers work) , it is commonly called phantom voltage as there is really no potential. Did you try and measure the voltage with the switch on? Also verify the breaker since this is all new to you someone may have turned this breaker off.