I don't think that location is supposed to have a circlip or snap ring of any kind; and the references of the manual seem to confirm that.
The 2 retaining clips (marked in red) in this system are there for the sole purpose of holding the central shaft (marked in blue) to the assembled joint. On the differential side, the left side is bolted while the right side just slides in, held in place by the dimensions of the rest of the suspension... Or does your axle have a groove for something on the trans/diff side? Can you post pictures since we don't have many axle jobs to reference?