IIRC it comes under the "
Communications failure prior to entering NAT oceanic airspace" section of Doc 7030.
Edit: Not where I thought it'd be, but here
http://www.faa.gov/air_traffic/publi...IGA%202004.pdf
pg 20:
If operating without a received and acknowledged oceanic clearance, the pilot shall enter oceanic airspace at the first oceanic entry point, level and speed, as contained in the filed flight plan and proceed via the filed flight plan route to landfall. That first oceanic level and speed shall be maintained to landfall.
Replicated (more or less word for word) in our own MATS Pt 2.
Couldn't find it in the online versions of Doc 7030 NAT 3.5.2.3 or P-ATM Doc 4444 Chapter 15 however.