Sadness everywhere

I went to pick up milk and crap at the market and made a beeline for the shortest line. I hate going to S&S, they're expensive but it's the 24 hour one and close to home. Sundays here suck because everything closes at six.
There was one woman in line, all her things on the conveyor belt already. I started to glance at the tabloids, reading about Brit-Brit binging and purging, Angie collapsing and other tales of woe (yeah...) in Hollywood.
The woman in front of me was making small talk with the cashier. The cashier was a middle aged Spanish woman, heavy accent. The woman in front of me was older, maybe sixties, Russian accent.
"I'm buying all this junk for my grandkids, they're coming to spend the night"
"Oh, yeah. how nice."
"Yeah, I got four now. Another on the way, but now just four."
"oh, wow. Your hands are full tonight."
"Oh, yeah, but I love it. I love when they come over. You got grandbabies?"
"I had two, but now just one."
I didn't want her to continue, how rude would it have been of me to jump the counter and cover her mouth with my hand. I saw the look on her face change, I saw the sadness come over her eyes. I saw the twitch at the corner of her lips.
"Oh?"
"Yeah, my granddaughter passed. Just seven months she was..."
The Russian woman stayed quiet, I could see she didn't know what to say, you could almost see the wheels in her head turning, looking for something to say...anything.
The cashier continued, "We didn't know what happened. They thought it was abuse and took my grandson from my daughter, he is three. Then the report came back saying she had something wrong with her intestine."
Oh, God.
The Russian woman was done paying. "I'm so sorry." she said and hurried away.
Did the cashier know I heard? What should I say?
"Hi, how are you today?" She asked me in an accent not too different from my mother's.
I smiled and spoke in Spanish.
I didn't mention the granddaughter, though I wanted to.
My heart broke into a thousand pieces when she had said what happened, and here I was paying for baby food and wipes.
Life isn't fair to people.