I found it! The introductory post for that mystery quilt is post # 595, on this page:
Birthday Swap 2018/2019 New
From there she gives the start date, and the following clues are given every two weeks thereafter. Originally she said every three weeks, but then shortened it to two. So if you want to find the pattern 'clues', just scroll through for posts from BarbaraKibbler, every two weeks after the start date.