the technology that has allowed for a life without livestock has failed
That would be the ability to grow crops? So only wild plants would grow for some reason? Impossible to farm anything then really, only viable lifestyles are scavenging, foraging and hunting
So, even if we're in a future form of humanity and all of our present farming methods failed, sowing seeds and harvesting crops would be the first kind of farming to be "restored" or "rediscovered" or whatever, because it's vastly more efficient, and assuming you're recovering from some sort of disaster scenario, feeding as many people as quickly as possible would probably be the goal. They'd probably grow rice and soy or something.
Animal farming is really for luxury goods, except in very remote places where crops can't be grown