I am very sorry to hear of your little dog's plight. I know that you must be extremely frustrated and worried.
To answer your question directly, I can't recall ever seeing any documented evidence to suggest that adhesions are caused by surgical error. Adhesions usually form when there is some sort of trauma to the organ involved. The uterus gets a little 'angry' and inflamed, and inflammatory reaction sets up on the uterus, but if the uterus is in contact with the abdominal wall, the inflammation involves both. This causes the two to become adhered.
When reading your post, I wonder if maybe your dog has had a little neurologic damage. If she had been straining hard for a period of time, or if the puppy were very large and pressing on the body wall in just the right (wrong?) way, there may have been some inflammation along the nerves, leading to her not urinating and being uncomfortable. The bloody diarrhea can conceivably be a result of the stress of the attempted natural birth and the c-section, along with changing hormones.
I hope that this is somewhat helpful. Good luck with your little girl. Please do not hesitate to reply if there are any other questions or concerns that I might help with.
I have heard of wrapping the organs in some of the mesentary to prevent adhesions, but this is usually done when there is a concern that they will occur (for instance in a chronically inflamed organ, or one that has had multiple surgeries). I cannot recall having seen a veterinarian in general practice perform this procedure.
I hope that this resolves the problem. Good luck with her.