The Body in the Black Box

[Lesley]

Hi everybody! 
Does anybody know anything about "The Body in the Black Box"? I don't recall reading about it in LB (but it is very possible that I forgot about it... if so sorry! ) and I was reading Hide and Seek with Angels and I am interested in that motive, the taking over the shadow / the identity. I googled it and found it nowhere, also on this page and in the forum - nothing. Is it unpublished? I didn't get it from HSwA it just said that nobody wanted it... did he publish it himself? is it possible to read the manuscript online? Grateful for any hints or tips! Thank you already!
Lesley