When Yoda was a Padawan, could the Jedi have thought he was the Chosen One?
It is highly doubtful that the Jedi would have considered the possibility that Yoda was the Chosen One.
In the time of greatest despair,
a child shall be born
who will destroy the Sith
and bring balance to the Force.
Yoda was born approximately 900 years before the events of the movies. However, the Sith were thought to have gone extinct about 1,000 years before the events of the movies (when Darth Bane created the Rule of Two).
Consequently, Yoda was born at a time in which the Sith were thought to be extinct, and Yoda was well past childhood by the time the Jedi learned that the Sith were not extinct. Yoda did not fit the description of the prophecy, so the Jedi probably never thought he was the Chosen One.