Do LATCC Mill actually have a strip with a FPL route on it when dealing with Civvy traffic. Used to deal with them on a regular basis on the east caost and they often didn't have a clue if I asked for a short cut to a another waypoint for weather avoidance for example. They also used to try and give us airway joining clearance for a airway that was not open!!
There will always be an electronic 'strip' available to Lon Mil controllers. This may or may not be the FPL that you filed. If your filed plan was not addressed to Lon Mil (EGWDZQZX) or did not get through the Mil computer's very strict syntax checking then 'your' plan will not be available. In this instance, a plan will be made up on the spot by the military support controller using whatever information is available. It may not always be recognized by the controller whether the 'strip' they are looking at has been filed by the operator or made up by the support controller. That is if the controller even bothers to read the routing info on the 'strip'. These 'strips' are used primarily for internal coordination and stats gathering. Controllers generally pay little regard to the route element and will rely on what they have been told by the previous controller or quiz the pilot. It should be noted that unlike IFPS, the Mil flightplan reception computer will
not issue the originator a rejection message if your plan fails automatic processing. There is no facility for manual handling of rejected plans. (Or rather there is but nobody does it).
As regards issuing a clearance for a closed airway, well, we don't issue them we just relay them. Sounds like the controller confused acceptance of a class G prenote by SCATCC with a clearance. No excuse there really.