I don't think this one is the one you're looking for because it doesn't contain that line but it expresses a similar sentiment.
Don't let them say, I wasn't born
That something stopped my heart
I felt each tender squeeze you gave
I've loved you from the start.
Although my body you can't hold,
It doesn't mean I'm gone.
This world was worthy, not, of me
God chose that I move on.
I know the pain that drowns your soul,
What you are forced to face.
You have my word, I'll fill your arms
Someday we will embrace.
You'll hear that it was "meant to be,
God doesn't make mistakes"
But that won't soften your worst blow..
Or make your heart not ache.
I'm watching over all you do,
another child you'll bear.
Believe me when I say to you,
That I am always there.
There will come a time, I promise you
When you will hold my hand,
Stroke my face and kiss my lips
And then you'll understand.
Although, I've never breathed your air,
Or gazed into your eyes..
That doesn't mean I never "was"
An Angel Never Dies........
~Unknown
I found it here
grievingparents.com/Poems.html
I think I know the one you mean, just can't think of it.