Wikipedia claims he is buried in the cloister of the Cathedral.
This claim is supported by Wikipedia which reports that he is buried in the Cloister of the Cathedral. https://en.wikipedia.org/wiki/Fernando_P%C3%A9rez_de_Traba
See also:
https://en.wikipedia.org/wiki/Santiago_de_Compostela_Cathedral#Othe...
Barton, Simon (1997). The Aristocracy in Twelfth-century León and Castile. Cambridge: Cambridge University Press. ISBN 9780521497275. This book refers to a quote by Fernando's daughter that she would be buried with him at the Cathedral de Santiago de Compostela.
This is compelling evidence. I would appreciate it if you would check your records and, if you agree, make the correction. Fernando is my 28th great grandfather. I appreciate your efforts in recording the details of his life. Tom Hudson
Fernando Pérez de Traba, Conde de Trastámara