Postal mystery.

In November, my friend Jade stayed at my house after a night out. She left the next day and forgot her phone charger, so I said I'd send it to her through the post as obviously it was a necessity and I wasn't going to see her for a while. As promised, I sent it to her and she sent me a text to say she'd received it and thank you. I didn't think anything more of it. However, a few days ago, I arrived home to find the charger on the floor, having been posted back to me in exactly the same envelope that I'd sent it in, with a sticker on it saying "this item could not be delivered because it was not called for." Confused by this, I rang Jade to see if she had any idea what was going on. She said she still had the charger at her house, and had been using it since I sent it back to her. I honestly have no clue how the charger could be at her house but also have been delivered back to my house at the same time. Obviously it must be a simple case of phone charger cloning, or some sort of alien conspiracy. Either way, Royal Mail have some serious explaining to do.