Front Diff Output Shaft - URGENT advice?

[SVX ROO]

While doing a routine ball joint change, the left side diff output shaft dicided it liked the world outside the differential rather than inside. When the ball joint came undone the upright swung out to the side a bit more than I expected. When I tried to put the ball joint in place the half shaft was hanging way out from the diff. My first thought was that the half shaft had been installed without the roll pin. Nope, roll pin was in place but the diff' output shaft had pulled out of the diff and was hanging onto the half shaft by the roll pin.

Anybody have this experience?

I have knocked out the roll pin and separated the half shaft so I have room to work. The shaft came out far enough to see the splined opposite end of the shaft which is only about 6" long.

I looked at the parts cut sheets and it seems this shaft just slips into the splines of the differential. Is there supposed to be something holding it in? I don't see any sign of a seal on that shaft either but I had no leakage. Is there one?

Can I just slide it back in? And than refit the half shaft?

If not, what is the fix??