My Great Grandfather

My Great Grandfather William Pritchard was born in Bangor in1866 , he joined the RWF 2/6 battallion which was formed in1914 as a back up force for WW 1 and was disbanded in 1917 . He died in Bootle Liverpool on 4/11/1915 aged 49 .
His grave at Glanadda Bangor has the RWF insignia on it , with his rank , Private , and his Service Number 20102 , his name also appears on the War Memorial at Bangor . I am trying to find more information about him , his service record etc . I have made an application via the museum at Cernarfon Castle but they were not able to trace him they also told me his name is not on the Roll of Honour .
can anybody please help me find some information about him

regards

Edward Pritchard