The answer to this mystery is described here: https://fotmd.com/forums/forum/site-questions-how-do-i/35300/mystery-solved-comment-walls-not-indexed-in-site-searches
Comments in Comment Walls are not indexed within site searches.
Discussion threads in Groups and Forums ARE included in site searches for phrases.
The word phrases were used in an FOTMD discussion, but not a discussion created by the person that posted what I was hunting for, so I should have said it was, as Strumelia suspected, a long comment. I'm not absolutely sure that it was Greg who posted it. He (Greg or someone else) was explaining to someone firstly that the name of a mode is determined by which note falls at the point at which the mode begins, & the key signature note is determined by which note falls at the 3rd fret. At the end of the posted comment he described Parallel Modes and Relative Modes. I'd like to re-read the whole thing.
Thanks SaltSprings! That explains the mystery- the word phrases Anne was searching this site for weren't actually used in that fotmd discussion... but rather they appear on the other site... the site that was linked to by Greg. 
That's why they didn't turn up in any searches of this site.
https://fotmd.com/strumelia/group_discuss/1042/great-resource-for-music-theory-group
Go to the link............tobyrush..........there are charts and the distinction between parallel and relative that Gregg posted.
Anne, I'm not having luck finding those terms either. I also did a search of Greg's activity feed for those terms and had no luck doing that. Not sure what else I can do! Are you positive that it was here on FOTMD that you read that post? I'm thinking that the post was actually a COMMENT on an item like a video maybe, and it's possible that Comments don't show up in search results.
Several month ago I read a post that talked of parallel modes and relative modes. I wanted to re-read it. Thought it may have been a response to someone by Greg Gunner, but am not sure. I've put in the search box both parallel modes and relative modes and neither has brought up the post I'm looking for. How can I find what I'm looking for?
Thanks, Ann
