What is Lost by Ilsa J. Bick

John Worthy knows a thing or two about loss.

For starters, he’s a fiction. A made-up man. A phony with a past spun out of thin air. He’s lost his parents, his brother, the place he called home. John isn’t even his real name. Before he was John, he was Danny. Before he was Danny, he was just a freaked-out kid with a singular talent: a boy forced to make an impossible choice.
Now, an Army surgeon, he’s a loner—until he meets Roni Keller. The daughter of a Marine, Roni is stubborn, determined, a fearless physician. Closer than friends, not quite lovers, they are deployed to assist in the U.S. evacuation from Afghanistan…
Where he makes a single, fatal mistake during an unsanctioned mission which costs Roni her life. Where John loses everything, even Roni’s remains which are never found.
Adrift, broken, John has checked into Brighter Days, a rehabilitation ranch for wounded warriors, and remade himself—again. He’s ready to leave when, out of the blue, Hank Patterson, a man he’s never met, shows up with an offer: return to Afghanistan with Taz Davila on a retrieval mission to recover Captain Keller’s remains from the forbidding mountainous terrain of the Wakhan Corridor, far to the northeast of Kabul.
How and why Roni’s body ended up hundreds of miles from where she died…no one knows. And just what is in the mountains that’s got the Russians—and even the Chinese—so interested?

In a race against time and enemies both known and hidden, John Worthy must confront present dangers and past demons to find redemption—and recover what he has lost.