When River Song finally escaped the Library and started searching for the Doctor, she kept hearing one terrible word: Trenzalore, Trenzalore, Trenzalore.
Her escape had been no miracle, but the culmination of centuries of hard work. Early on, the Lux Corporation exterminated the Vashta Nerada and secured DNA samples for its trapped (dead) employees. Cal, using her extraordinary computing power, began analyzing the DNA line by line, with River's help. When the analysis was completed several centuries later, they began to run experiments -- could Cal materialize a hand? A foot? An eyeball? After some initial gooey mistakes, they perfected and refined the procedure.
When they were confident Cal was ready, River volunteered to be first. The Lux Corporation brought in carefully measured blocks of raw materials: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus; and traces of potassium, sulfur, sodium, chlorine, and magnesium. Cal saved the raw materials into her system, re-encoded them to River's DNA, merged them with River's saved mind, and rematerialized the new body.
River had gasped as oxygen flowed into her new lungs, as her synapses fired and muscles contracted. She lived! It was a resounding success. The Lux Corporation physicians were slightly baffled at the odd energy signatures within her body, but decided it was harmless. What River did not tell them was that Cal's skill was even more profound than they imagined: she had also managed to restore a full Time Lord regeneration cycle into River.
Both River and Anita decided to be resurrected. Evangelista, the Daves, and Cal herself declined. They loved Cal's world, and reasoned that the people they knew in the physical world were long dead. There was no hurry -- they could change their minds later. But Anita was eager for a new adventure, and River just wanted out.
The thing that concerned River was that her resurrection had been brought about entirely by human ingenuity. As far as she could tell, the Doctor wasn't behind any of it. Worry consumed her mind as she pushed through physical therapy, impatiently learning to sit and walk and eat again with a familiar body that had never actually moved before.
Once declared fit by the physicians (and after signing a confidentiality agreement about the Lux Corporation's new resurrection machine), she collected her few remaining things: her diary and sonic screwdriver, which the Doctor had hidden in the Library nine hundred years earlier, and her vortex manipulator, which she had stored in a bank vault paid for over the centuries by the Rory and Amelia Williams Foundation of 1957. With nothing else but her wits, she immediately began to make quiet inquiries through the universe---where is the Doctor?
Dead, his enemies exulted. Gone, his allies mourned. And one whispered word, over and over and over: Trenzalore, Trenzalore, Trenzalore.
In desperation, she had listed their mutual friends in alphabetical order and started to contact each one, begging them to tell her that he'd seen her just one more time. I'm so, so sorry, they would say. He'd gone to Trenzalore a widower, and perhaps embraced his death a little easier for it. It hurt too badly to keep hearing, and so she stopped asking before she reached "V: Madame Vastra."
It was fixed. She would never see him again.
Oh, River wept. She wept so bitterly, for she was too late. Before she chose to leave the Library, she knew this was a possibility. She well remembered saying goodbye to him at his tomb, his kiss lingering on her data-ghost lips. See you around, Professor River Song, he'd lied. She had feared the possibility that he'd caught up with that tomb before she could escape the Library, but had hoped otherwise. Hoped in vain. And so she had curled up at the end of the universe and wept for herself, and her thirteen new lives without him. For him, and his tears at Darillium. For them, and all that they could have been. For the Tardis, the beautiful Tardis, which would have died with him.
Then, her tears spent, she dusted herself off and went to rebuild her life. Luna University was delighted to have her back. It was highly irregular, but they reasoned that a thousand year old professor (ha! if only they knew) was a tremendous addition to to archeology department. She taught eager young students, and was known as the best and most terrifying professor at the university. She collected first editions of her mother's books. Made sure she had a weekly chat with Cal through the Galactic Inter-Library Loan Link. Went on digs. Drank fine wine. Took creative lovers to her bed. Avenged the Doctor by hunting Daleks during university holidays.
She would miss him forever, but it was a good life, and she was glad to have it back.