Ina Adeer, an event of such magnitude like the coming of Mahdi would have been mentioned and included in the Quraan, but there is none. Let us leave there.
About the return of Jesus PBUH, he has been mentioned many times in the Quraan to explain who he was, his elevation and of his return which the Hadiths illuminate and describe further.
Allah SWT Knows Best
Well, if we follow your line, Muslims will never be able to identify the return of Jesus, the Son of Mary, (peace be upon him). The only person who will be able to identify him is Imaamul Mahdi.
Evidence from Quran about the Second Coming of Jesus عليه السلام
4:159. وَإِن مِّنْ أَهْلِ الْكِتَابِ إِلاَّ لَيُؤْمِنَنَّ بِهِ قَبْلَ مَوْتِهِ وَيَوْمَ الْقِيَامَةِ يَكُونُ عَلَيْهِمْ شَهِيدًا
Allah (God) says in the Quran, "There shall not be anyone from People of the Book, but shall believe in him before his death and on the Day of Resurrection, he (Jesus) shall be a witness against them." (Quran 4: 159)
Furthermore, Allah (God) also says in the Quran, "And he (Jesus عليه السلام) shall be a Sign (for the coming of) the Hour (of Resurrection); therefore have no doubt about it (the Hour). And follow me (Allah), this is a Straight Path." (Quran 43: 61)
Abdullah. Ibn Masood reported that the Prophet صلى الله عليه وسلم said, "Even if there remains only a day before the World ends, the almighty Allah will greatly prolong that day to send a man from me (my progeny), from members of my House (family).
His name will be similar to my name and his father's name similar to my father's name. He will fill the Earth with equity (fairness) and justice, as it (previously) was filled with oppression and injustice." (Abu Dawud)
The holy Prophet (SAW) said: "A group of my Ummah will fight for the truth until near the day of judgment when Jesus, the son of Marry, will descend, and the leader of them will ask him to lead the prayer
, but Jesus declines, saying: "No, Verily, among you Allah has made leaders for others and He has bestowed his bounty upon them."" (Sahih Muslim)
It is reported from Abu Hurayra (RA) that the Prophet (SAW) said: "What will be your reaction when the son of Mary (Jesus) [pbuh] descends and your Imam is from among yourselves
? (Sahih Muslim, bab nuzul 'isa, Vol. 2; Sahih Bukhari, kitab bad' al-khalq wa nuzul 'isa, Vol. 4)
The holy Prophet (SAW) said: What would be your situation if the Son of Mary (i.e. Jesus) descends upon you and your Imam
is from among you? (Bukhari, kitabul-Anbiya, Chapter Nuzul Isa bin Maryam)
The question that I have for you and others with similar view is: how will you identify the return of Jesus, the Son of Mary, (peace be upon him), if you don't believe in Imamul Mahdi and authentic hadiths that prophesied him?
Btw, there are many more hadiths that discuss Imamul Mahdi.
The word Mahdi (Mehdi) means a rightly guided leader.
Remember authentic hadiths provide details in order to understand the Holy Quran!