Psalms Scroll (Non-Canonical)

This is what is written in the Psalms Scroll which is not in our texts. I wonder why this was left out? Here is what the text says:

Column 19: Plea for Deliverance (A Noncanonical Psalm)

Surely a maggot cannot praise thee nor a grave worm recount thy loving-kindness.
But the living can praise thee, even those who stumble can laud thee.
In revealing thy kindness to them and by thy righteousness thou dost enlighten them.
For in thy hand is the soul of every living thing; the breath of all flesh hast thou given.
Deal with us, O LORD, according to thy goodness, according to thy great mercy, and according to thy many righteous deeds.
The LORD has heeded the voice of those who love his name and has not deprived them of his loving-kindness.
Blessed be the LORD, who executes righteous deeds, crowning his saints with loving-kindness and mercy.
My soul cries out to praise thy name, to sing high praises for thy loving deeds, to proclaim thy faithfulness--of praise of thee there is no end.
Near death was I for my sins, and my iniquities have sold me to the grave; but thou didst save me, O LORD, according to thy great mercy, and according to thy many righteous deeds.
Indeed have I loved thy name, and in thy protection have I found refuge.
When I remember thy might my heart is brave, and upon thy mercies do I lean.
Forgive my sin, O LORD, and purify me from my iniquity.
Vouchsafe me a spirit of faith and knowledge, and let me not be dishonored in ruin.
Let not Satan rule over me, nor an unclean spirit; neither let pain nor the evil inclination take possession of my bones.
For thou, O LORD, art my praise, and in thee do I hope all the day.
Let my brothers rejoice with me and the house of my father, who are astonished by the raciousness...
[ ] For e[ver] I will rejoice in thee.