Before going out and making a new rod, you may want to determine why the existing rod was able to virtually fall out.
It's hard for me to picture exactly what happened.

Do you mean that the rod was adjusted so far out that there was no adjustment threads) left? If that's the case, find out why you are out of adjustment. I haven't had that happen on a 122, but on 2 of my early 140s, the clutch arm bent through normal use. I ran out of adjustment is how I found out they were bent. Apparently Volvo figured it out too because they changed the design of the clutch fork in '70 or '71.

But now that I think of it, the 122 has a "push" type of clutch fork as opposed to a 140 which has a "pull". Not sure if that would make a difference.
Anyway, try to inspect your fork for a bend.