Could you give a few more details? Are you maybe using a stack mod?

i am in the same boat, i hit level 100 and it shows i unlocked the engram but cant find it in the craft menu. i use the ultra stack mod, does that prevent me from finding it?

the stack mod might affect it in some way, what map are you on?

rag, it showed up the next day, now im dealing with the egg disappearing while its incubating.

Never mind on the disappearing, my mate put down a hatchery and didnt tell me so it just kept collecting the egg lol