The tribe of Daus has disobeyed (Allah and His Apostle) and...
The tribe of Daus has disobeyed (Allah and His Apostle) and refused (to embrace Islam), therefore, invoke Allah's wrath for them." The people thought that the Prophet would invoke Allah's wrath for them, but he said, "O Allah! Guide the tribe Of Daus and let them come to us," Rasulullah was a mercy for mankind and it was part of his great compassion that he made du'as of guidance to the truth for all people, including the mushrikeen.
Praying for their guidance should not in any way be deemed as a virtue of the mushrikeen. It was an example of Rasulullah's desire that ALL are guided. So even if Rasulullah (s) did for arguments sake pray for Mu'awiya's guidance, it was in the same way as he prayed for all to be guided to the right path whether Muslim or non Muslim.
Not all of Rasulullah's prayers were accepted Even if for arguments sake we were to accept this dua, according to Ahl'ul Sunnah not all of Rasulullah's supplications were accepted by Allah (swt). Ibn Hajar Asqalani in Fathul Bari Volume 11 page 97 states: "If the Prophet (s) makes a dua for his Ummah it is accepted by Allah (swt) whereas if he makes it for a particular individual it may or may not be accepted".
So even if we are to accept this dua for arguments sake, to be Sahih, whether or not it will be accepted is subject to Allah (swt)'s discretion.
With regards to Mu'awiya, his 'noble' deeds make it clear that Allah (swt) would never deem him as a Guide, and to prove this, let us see the words of Allah (swt) Allah (swt) never guides a wrongdoer We read in Surah Tauba verse 80: Whether thou ask for their forgiveness or not (their sin is unforgivable): if thou ask seventy times for their forgiveness Allah will not forgive them: because they have rejected Allah and His apostle; and Allah guideth not those who are perversely rebellious (Zalimoon) [Taken from Abdullah Yusuf Ali's translation of the Qur'an].
Abdullah Yusuf Ali's comments in the footnotes of this verse are indeed interesting: "An awful warning for those who actively oppose the Cause of Allah. The Holy Prophet was by nature full of mercy and forgiveness. He prayed for his enemies. But in such a case even his prayers are nullified by their attitude of rejecting Allah". We suggest our readers contemplate this verse in light of Islamic history.
There is no possibility that Mu'awiya was even remotely a Hadi who guided others on account of his guidance.