A considerable time before they got stuck in the snow, when it became clear that they wouldn't have enough food, they sent a couple of men on horseback to bring back more. They showed up not too long after they made camp at what would become Donner Lake.
Donner Lake, on this side of the pass? So, they did not
accomplish their mission?
I remember Mr Reed, after being expelled, rode his horse
the long way around and got help.

[i]While they didn't have any skis one of the men made snowshoes and the strongest of the men and women tried to make it across with six day's starvation ration. On that trip they got lost in a snowstorm, people froze to death, and they ate the two indians, Lois and Salvatore, but word got out. [/i]
So I did remember correctly about the Indians.
None of this party ever made it all the way to civilization?
Edit: I see "word got out", so they made contact.

One of the major issues was that people assumed that the group had a normal compliment of oxen to eat. They didn't know that the salt flats and indians had reduced the numbers available. Hard to replace the food on the hoof a full sized oxen represents with what you can haul on a horse. Even counting the horse.
The narrator said they had lost cattle to Indians, but I
assumed they had (early on) enough to supply their own
recon party. I never heard of preps, like making snow-shoes
or jerking meat. Did they wait too long, before sending the
recon party?
Are you saying that the locals, near the Pacific Coast,
knew they were stranded, but said "Let them eat cattle".

This casts a whole different light on things.

The other thing is that the weather was extraordinarily difficult. The number and intensity of the storms broke records.
Yes, that was a killer. There is a lesson. It is a big risk
waiting for a spell of good weather, because it might or
might not come.