Undoubtedly, there exists the possibility of meeting Hazrat Mahdi (a.t.f.s.) during the major concealment. The best proof is the occurrence of such incidents in the length of history of the major concealment. The writings of scholars of Hadith , right from the oldest books till the current ones, are full of narrations about such meetings that have occurred during minor and major concealment period.
The vital point lies here that whether such meetings and contacts occur as per our wish and intention, or the discretion lies with Hazrat Mahdi (a.t.f.s.)?
Experience reveals as well as the sentence of Imam’s ‘Tauqee’ addressed to Ali-ibn-Muhammad Samiri shows that such contacts occur due to Imam’s will and permission and not because of people’s wish. This is exactly one of the meanings of minor and major concealment (‘Ghaibat’). That which has been negated in Imam’s ‘Tauqee’ is bilateral contacts by the will of the common people (so that the door of deputyship etc is closed).
In ‘Tauqee’ we find these words:
“’Zuhoor’ (Reappearance) wouldn’t occur except if the Almighty Allah gives permission” which shows that there wouldn’t be any ‘Zuhoor’ (manifestation) except if Allah wishes. Such type of meeting is negated otherwise there isn’t the least doubt about the direct unlimited favours and generosities of Imam (a.t.f.s.) whether apparent or concealed to the common man in general and his Shias in particular.
To conclude, in conformation of the fact that Imam Mahdi (a.t.f.s.) constantly exhibits his favours to his Shias and sometimes even manifests himself, we set forth here a sentence from Imam’s ‘Tauqee’ to Shaikh Mufid:
“We have news about you. We are aware of your hardships and we are not neglectful in observing your state. We aren’t forgetful of you, otherwise you would live a difficult life and the enemies would destroy you.” 
Observance, remembrance, and collection of news constantly occur together with apparent favours and grace. In one quick and short research one can see that the most pious and trustworthy figures in history like Sayyed Bah’rul Ulum, Allamah Hilli, Muqaddas Ardebeli and many others have succeeded in meeting Hazrat Mahdi (a.t.f.s.) thus leaving no place for any doubt.