in the history of the order...
1011 1149 Stonehenge: The now Nameless Covenant, in Anglesey, is destroyed in one of the last major conflicts of the Schism War. Quaesitores investigating the covenant’s remains find something or some things in the ruins that lead them to obliterate the site entirely and destroy most of its records. [HtM]
Looks like you have a similar situation but they got a bit sloppy in the cover up