R. Yehdai Gaon writes (year 760):
For more than one hundred years both yeshivas (Pumbedusa & Sura) hasn't been learning Meseches Nedarim.
When the first Shas was printed by R. Yehoshua Shlomo and his son R Gershom Soncino , they printed only those Mesechtos the Yeshivos were learning.
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Meseches Nedarim was not printed because it was one of the Mesechtos not learned in the Yeshivos.
Meseches Nedarim was neglected for about 800 years.
אנן לא גרסינן נדרים ולא ידעינן לאסור ולהתיר בהלא נדר
ולא שבועה (ר' יהודאי גאון )
It was a non-Jew, Danille Bomberg* the first one, to print the complete Shas** including Mesechta Nedarim.
Only after the printing of the Bomberg Shas , did Meseches Nedarim become part of Shas and Yeshivos started learning it.
If not for Bomberg, Mesechta Nedarim might not have been part of the Daf of today.
*born in Antwerp Belgium
** printed in Venice 1520 -23