It could be the one by Mary Stevenson ...
Footprints in the Sand
One night I dreamed I was walking along the beach with the Lord.
Many scenes from my life flashed across the sky.
In each scene I noticed footprints in the sand.
Sometimes there were two sets of footprints,
other times there were one set of footprints.
This bothered me because I noticed
that during the low periods of my life,
when I was suffering from
anguish, sorrow or defeat,
I could see only one set of footprints.
So I said to the Lord,
�You promised me Lord,
that if I followed you,
you would walk with me always.
But I have noticed that during the most trying periods of my life
there have only been one set of footprints in the sand.
Why, when I needed you most, you have not been there for me?�
The Lord replied,
�The times when you have seen only one set of footprints in the sand,
is when I carried you.�
http://www.footprints-inthe-sand.com/