Kind of close to home for me in the last year. Here's the story.
We have a really good friend and customer from out in Eastern Kansas that called last year concerning a very good Shorty cow that had done about this same thing. Due in March but nothing, local vet's and ET guy all said she was bred, that they must of just been WAY off on thier breeding date.
Not the case, after some discussions, they brought the cow here. She was , on palpation, carrying a 90-110 day mummy, as well as being bad cystic as well. We treated this cow as if you were trying to induce labor, and in 5 days she had the mummy pushed up into the cervix, but could not get any further due to lack of fluid and volume to push against.
Thru vaginal intervention, I simply got hold of it and yanked it out. It was 8 plus pounds of solid white matter, not rock hard but very firm. Surprisingly , it did not have a bad odor, just dry and hard. I infused this cow many times over the next week, and worked on the cystic condition of her ovaries.
Here is the good part -- after 2 weeks, she managed to get rid of her cysts, and showed a good heat. Normal activity. Me being rather oportunistic, I went and bred the cow just to see what would happen, and did a single egg collection a week later. We DID get an egg -- althought it was degnerated -- we found the egg. Uterus was clean, and felt pretty darn good, so I supered the cow as you normally would.
Hehehehehe -- we froze 4 excellent embryos from that flush out of 6 produced, and then re-bred the cow on her first heat. Now get this --- she settled, went FULL term, and calved a large bull calf this spring, cow and calf doing great -- and she is now getting ready to be a donor again! I was and am very glad --
Bottom line -- although this is very rare and VERY serious, it is not the end of the world, it CAN be cured with diligence.
The causes???? Yes, it can be anything from heat stress at the wrong time clear up the disease issues and on into the nutritional end of it. I have seen them in every breed, more in the dairy cows than in beef, but surely in every breed there is. It will happen in about 1 in every 2500 cows, but MOST of them do get rid of it before it gets to the point of the one above. In your case, selling the cow of average value was probably the right thing to do, but if you get a real high dollar cow, you CAN get her thru it!
Food for thought -- I can give you the folks name and number if you re curious, I am sure they will tell you all about it!
PS -- The first one of those 4 embryos was transfered this spring out there, and has also apparently settled!!! How good is that?? hehehehehe