The nyxborn lynx stat block page says it's found on page 200 of the Basic Rules when it's actually from page 200 of Mythic Odysseys of Theros.

I believe you are correct

But I checked and it's not there 

You checked what, and what’s not where?

I checked if the nyxborn lynx was in mythic Odysseys of theros and did not find it

Well, part of the problem might be that the link you posted leads to the magic items from that book, and the nyxborn lynx is a monster. Also, the book doesn’t provide a statblock for each and every nyxborn creature, just rules for how to add nyxborn stuff to creatures from the monster manual. See:

https://www.dndbeyond.com/sources/moot/friends-and-foes#NyxbornCreatures