I must presume that you walk in the Colchester area as that is the info that comes up googling 'OS Map E.168'. For most of us here a map reference might be a bit more helpful.
From my time on a LAF, the classification of unclassified roads was so complex that it mostly passed over my head, but understanding the term 'lostway' is more simple, if those, who should be interested would apply a bit of simple logic to it.
As far as the bureaucracy and thus the establishment will interpret it, it is a way once used that is recoverable by the process of law. Proof required can be found by contacting your rights of way depts. at town hall and if you prodded the Ramblers Association enough they would come up with it.
I think it might be on their website as they are supposed to running a campaign for "discovering lostways".
I think there is a much simpler way of understanding lostways; The creation of the Definitive Map as provided for by an Act of Parliament in 1949 was corrupted by many of the officials and bodies charged with it's formation. By comparing the pre-war editions of the OS maps going back to the early 1880's a snapshot in time is recorded how people accessed many destinations and features, which are compatible with the intentions of the 1949 Act.
Why were these ways left off the definitive maps of our counties?
Too often it all to obvious that the part of the map that appears not to have any RoW's are too the advantage of particular owner's of land. An old unclassified road, fallen into disrepair, is probably possible too re-instate if enough pressure and legal proof is collected pre 2026, but each application will be the subject of a separate inquiry set up by a government inspector.
I do not believe the timescale between now and 2026 gives enough time to repair our access network from the damage done to it by landowners and their agents, supported by sympathetic local authorities.
If your Class 5 road could add benefit to the access network both socially and economically then people should know about it. Your local authority should be asked why it is not on the definitive map.
Another route might be to bring it to the attention of the British Horse Society, they have a more effective campaign and are more likely to be sympathetic to people who are not paying members of their organisation. But they would be more interested in routes that are recoverable as Bridleways, this is compatible with a defunct road.