Firstly: 

If what is meant is the du‘aa’ that is published widely in many chatrooms and on many websites under the name “al-du‘aa’ al-mustajaab”, which is attributed to a report that says that ‘Umar ibn al-Khattaab and ‘Ali ibn Abi Taalib (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever offer ssupplication calling upon Allah by these names, He will answer his supplication: ‘O Allah, You are the Ever Living Who never dies, the Creator Who never is overcome, the All-Seeing Who is never in doubt, the All-Hearing Who is never uncertain, the Truthful One Who never lies…’”… To the end of the lengthy hadeeth: 

This is a fabricated a du‘aa’ that is falsely attributed to the Messenger of Allah (blessings and peace of Allah be upon him) and there is no saheeh hadeeth that speaks of its virtue. It is not permissible for any Muslim to transmit it on the basis of it being a hadeeth from the Messenger of Allah (blessings and peace of Allah be upon him). We have previously discussed this in detail on our website, in the answer to question no. 116137. 

Secondly, 

If what this sister is referring to is the book which is called ad-Du‘aa’ al-Mustajaab, it is also an unreliable book which includes many fabricated hadeeths and a number of things that are contrary to sharee‘ah, hence the scholars have warned people against it. 

In Fataawa al-Lajnah ad-Daa’imah (2/449) it says: 

This book – ad-Du‘aa’ al-Mustajaab – cannot be relied upon because it contains a large number of weak (da‘eef) and fabricated (mawdoo‘) hadeeths. End quote. 

‘Abd al-‘Azeez ibn ‘Abdullah ibn Baaz, ‘Abd ar-Razzaaq ‘Afeefi, ‘Abdullah ibn Ghadyaan, ‘Abdullah ibn Qa‘ood. 

Shaykh Ibn Baaz (may Allah have mercy on him) said: 

It is a book that cannot be relied upon and its author is not a scholar. Hence we have been drawing attention to this for a long time and we have stated that this book cannot be relied upon. Readers should be alerted to the fact that it cannot be relied upon because of what it contains of weak and fabricated hadeeths. 

Fataawa Ibn Baaz, 26/354-355 

Shaykh Saalih al-Fawzaan (may Allah preserve him) said: 

There is a book that is widely circulated among people today and is available in bookstores. It is called ad-Du‘aa’ al-Mustajaab, by Muhammad ‘Abd al-Jawaad. It is a book of myths which includes innovated Sufi du‘aa’s and dhikrs which are quoted without any evidence for that from the Qur’aan and Sunnah. Its title is an audacious statement about Allah, may He be glorified and exalted, because the book is called ad-Du‘aa’ al-Mustajaab (the supplication that is answered). But who is the one who told him that this supplication is answered? What evidence is there for that, except that he wanted to attract the attention of the common folk and deceive them with this fabricated book. I refer the reader to some trustworthy books of du‘aa’s and dhikrs that were written by leading, trustworthy Sunni scholars: 

1.     al-Waabil as-Sayyib by al-‘Allaamah ibn al-Qayyim

2.     al-Kalim at-Tayyib by Shaykh al-Islam Ibn Taymiyah

3.     al-Adhkaar by Imam an-Nawawi 

These books do not contain any innovated dhikrs; they do contain dhikrs narrated in the Qur’aan and Sunnah. They are sufficient and there is no need for books of myths written by jokers, praise be to Allah. 

End quote from Majmoo‘ Fataawa Fadeelat ash-Shaykh Saalih ibn Fawzaan, 2/697 

You could also refer to what is quoted on our website in the answer to question no. 13506, where we discussed the conditions of du‘aa’ being answered and the means of having one’s supplication accepted by Allah, may He be exalted. 

And Allah knows best.