What do you find?
Nothing. Not a trace of the festival.
I know that tradition records that Rabbi Akiva’s vast numbers of students, fighting against the Romans, were smitten by a plague (Talmud Yevamot 61b) that lifted on this day. But the institution of Lag Ba’Omer as an official holyday took time to emerge.
Not until the 13th century is there a literary source, when the Sefer HaManhig (91b) reports a saying of Ibn Yar’chi that the ban on marriages during the Omer is relaxed on and from the 33rd day of the S’firah.
One explanation may be that as the weeks of the Omer proceeded, their severe impact waned and custom took account of what people were doing. Whether this is the truth or not, it indicates that the people had an effect on the development of the observances of Judaism. Another example is of course Simchat Torah.