These two studies may be of interest
Ramachandran, V. S. "Phantom Penises in Transsexuals." *Journal of
Consciousness Studies *15 (2008): 5-16.
and
Ramachandran, V. S., and P. D. McGeoch. "Occurrence of Phantom Genitalia
after Gender Reassignment Surgery." [In eng]. *Med Hypotheses *69, no. 5
(2007): 1001-3.
I think they are available in Google Scholar