SOLVED. Middle-Grade or YA Science Fiction about a Dystopia with food scarcity and rationing, focuses on two young teens, male and female as they become part of a plan to improve life, though they aren't sure what the plan is. Read mid-late 1970s.

[Christopher]

I read this in the mid-late seventies, and believe it was published then. I remember that the male character had somehow taught himself about farming, and the both his and the female lead's families had disappeared, but both were pretending their families were still around in order to get their food rations, which still were not really enough. Each was contacted by a person who reinforced that they must continue their masquerade, but who made them forget the actual contact each time. The only other detail that I am sure about was that the entry to the method of survival (no, I don't recall what it was) required the element mercury to access.

[Rainbowheart]

The Missing Persons League

[Christopher]

Rainbowheart wrote: "The Missing Persons League"
THAT IS IT! Thank you, VERY much!

[Rainbowheart]

You're super welcome, glad to help out!