“The police are looking for you.” That’s what a friend told me 15 years ago today — Aug. 3, 2004 — as I relaxed inside Little Wound High School in Kyle, S.D. Instantly, I knew my daughter Sara in suburban Los Angeles had at last given birth to my first grandchild.

I was on a church mission trip in Kyle, where the Oglala Lakota Sioux live on the Pine Ridge Indian Reservation.

I was with 33 teens and six chaperones who had departed from our suburban Cleveland church in an angry rain at 3:30 a.m. July 31 and driven 1,300 miles to Kyle. When we arrived at sundown Sunday, Aug. 1, nobody was there to welcome us. They were at the tribe’s Sun Dance somewhere far out on the prairie.

Sara and husband Peter’s baby was due July 31, but it was not born that day, or Aug. 1, or Aug. 2, either. As I hung drywall and painted at the Partnership in Housing project, my mind wandered and wondered.

Then, on Tuesday evening, after our sobering visit to Wounded Knee, a friend said the police were trying to find me. I had no cellphone, so she handed me one. I headed off to a private spot and called the police. I learned that my niece in Cleveland — unable to call the church because its offices were closed — had called them to say that Sara had delivered her son in the late afternoon. She asked them to find me.

I called Sara. When at last I heard her tired but euphoric voice from so far away, I cried. I worked with joy the rest of the week.

As brutal gusts scoured the prairie, I would stop painting, cling to the ladder and wait for the wind to pass, and think of that precious new life 1,500 miles away. I watched the solitary tree that sprouted out of a gully on the prairie, and the few wildflowers that bowed to the wind. Life was so precious, not just in California but here on the Oglala Lakota’s reservation, too.

When we suburbanites peered out of our air-conditioned vans when we’d arrived Sunday, we saw ramshackle trailers and battered cars and unleashed dogs. Alcoholism and drug use were rampant, we’d learned.

But beneath that grit were fascinating people with plenty to teach us. Lyle, for example, was our witty, wise project manager. Half white and half Sioux, Lyle had worked construction all over the West. He was frustrated because unemployed tribe members did not help build these houses. They left that to white volunteers like us.

Jim, who worked in the kitchen at Little Wound High School, told us that the tribe keeps a herd of buffalo. When a tribal member dies, the tribe slaughters a buffalo and makes buffalo stew.

Mercy, a kitchen worker with dancing eyes, arrived at 7 one morning to make us Indian fry bread.

We influenced the natives, too. Some of our group painted the walls of Little Wound High School. The more we painted, the more inspired the Lakota painters became. Instead of leaving soaked paintbrushes in the halls at night, they began to clean up like we did.

On the way home, we stopped in Sioux Falls, S.D., and met the Rev. Joseph Dudley. He had written a quietly eloquent book, “Choteau Creek,” about growing up with his grandparents on the Yankton Sioux reservation. The book doesn’t dwell on poverty or Dudley’s two-mile walk to school or the chilling South Dakota blizzards. Instead it talks about Dudley’s grandparents and their kindness, their sharing, their belief in God.

“Were you lonely out there?” I asked Dudley, imagining a child dwarfed by that vast landscape.

“Never,” he answered quickly. “I made up imaginary friends.”

Life is hard up there, but there are intangible riches, too. That’s what I remember, along with the birth of Brendan, now 15, and the police who searched for me to share the news in that sparsely beautiful place.