The shifting nature of Reverie makes attempting to describe the location of a lost individual almost nonsensical. However, it does appear to be, in principle, possible to target a gate to their location even though you might not actually be able to describe that location. To do this, you need a way to establish some sort of link to their consciousness. This requires acquiring or creating some sort of physical object that is in some way connected to the targets, ideas, perceptions, creativity, thoughts, or imagination.
There was once a weaver who would always produce and leave behind a small wooden carving before travel to Reverie. His theory was that, as something he had created, the carving could be used as link to his creativity and could be used to find him.
Another account references a lost Weaver being found by friends. The Weaver repeatedly sent them numerous dreams always describing the same image: a peacock standing the stump of an oak tree backlit by the first sun of dawn. The friends were able to establish this link using a painting they had commissioned of the image. However, your research suggests that this only worked because they knew the Weaver was regularly contemplating that image.