I have no idea if this is based on any kind of true story but I imagine similar things happened throughout time.  Maybe it was Soldier Claudius or Crusader Althwulf.  Whomever it was, I'm sure their sorrow was as great as the other men who regretted impulsive actions and lost a sweetheart.

He was just a lonely cowboy,

With a heart so brave and true.

And he learned to love a maiden,

With eyes of heaven's own blue.

They learned to love each other,

And named their wedding day.

When a quarrel came between them,

And Jack, he rode away.

He joined a band of cowboys,

And vowed he'd forget her name.

Out on the lonely prairie,

She waited just the same.

Your sweetheart waits for you, Jack.

Your sweetheart waits for you.

Out on the lonely prairie,

Where skies are always blue.

One night when work was finished,

Just at the close of day,

Someone said sing a song Jack.

That'll drive all cares away.

But when he started singing,

His mind did wander back.

For he sang of a lonely maiden,

Who waited for her Jack.

Your sweetheart waits for you, Jack.

Your sweetheart waits for you.

Out on the lonely prairie,

Where skies are always blue.

He left the range next morning,

Breathing his sweetheart's name.

Said, "I'll go and ask forgiveness.

"For I know I was to blame."

But when he reached the prairie,

He found a new-made mound.

His friends they sadly told him,

They'd laid his sweetheart down.

Your sweetheart waits for you, Jack.

Your sweetheart waits for you.

Out on the lonely prairie,

Where skies are always blue.

A few years ago, I was looking for musical chords to these songs and found another verse that Dad never sang.  I imagine it goes after the "laid sweetheart down" and before the chorus.

They said as she was dying
She breathed her sweetheart's name
And asked them with her last breath
To tell him when he came

...thumble thum thum...