wht u say is not tht really true. The people knows about Imam Al-Mahdi in person is the people who already meets him, from the appereances' evidence that Prophet Muhammad S.A.W described in his hadiths. Imam Al-Mahdi will officially be announced at the age of 40years old, remember?

"After the death of a Ruler there will be some dispute between the people. At that time a citizen of Madina will flee (from Madina) and go to Makkah. While in Makkah, certain people will approach him between Hajr-ul Aswad and Maqaame Ibraheem, and forcefully pledge their allegiance to him. Thereafter a huge army will proceed from Syria to attack him but when they will be at Baida, which is between Makkah and Madina, they will be swallowed into the ground. On seeing this, the Abdaals of Shaam as well as large numbers of people from Iraq will come to him and pledge their allegiance to him. Then a person from the Quraish, whose uncle will be from the Bani Kalb tribe will send an army to attack him, only to be overpowered, by the will of Allah. This (defeated) army will be that of the Bani Kalb. Unfortunate indeed is he who does not receive a share from the booty of the Kalb. This person (Imam Mahdi) will distribute the spoils of war after the battle. He will lead the people according to the Sunnah and during his reign Islam will spread throughout the world. He will remain till seven years (since his emergence). He will pass away and the Muslims will perform his Janazah salaat." (Abu Dawood)

Look at the Syrian armies, they worship the Syrian president, Bashar Assad. It is evident that these syrian armies are against Allah s.w.t!