Those folks were referring to one of the many Russ Jolley trails. Mr. Jolley is a long time gorge enthusiast, hike leader, and author whose book "Wildflowers of the Columbia Gorge" is a masterpiece. He built numerous trails and the one up Horsetail Creek is one of them. It is currently seldom hiked and one of the many gorge "secrets" but obviously some are still aware of it and hike it. It is hard to follow in the upper reaches but is still in pretty good shape. From the Rock of Ages Ridge Trail you will never spot it but the markers, when you know them, are unmistakable. I'd be happy to lead a trek if anybody's in for a little abuse.
Here's a map:

Now, of course, all of you who are reading this and comtemplating a trip are on your honor to take loppers to help clear this trail! - and it needs it!
- Don
"If I had known I was going to live this long I'd have taken better care of myself" - anon