1968 is a tough yeast to rinse. It flocculates so much that it falls faster than the trub and hop matter. It should be the bottom layer, but often gets mixed in with the trub. You can save the top and bottom layer in separate jars if you're not certain which layer it is. I did this the first time I tried to rinse 1968, and for me it turned out the bottom layer than most of the yeast.