Nearly everywhere in the story of Samson, more than in most stories in Tanakh, both parents are mentioned quite frequently. Leading up to birth, both parents share about equal page-time. After birth, they are always mentioned together - "aviv v'imo", "his father and mother".
The only place this is not true is the last pasuk, 16:31:
וַיֵּרְדוּ אֶחָיו וְכָל-בֵּית אָבִיהוּ, וַיִּשְׂאוּ אֹתוֹ, וַיַּעֲלוּ וַיִּקְבְּרוּ אוֹתוֹ בֵּין צָרְעָה וּבֵין אֶשְׁתָּאֹל, בְּקֶבֶר מָנוֹחַ אָבִיו
Then his brethren and all the house of his father came down, and took him, and brought him up, and buried him between Zorah and Eshtaol in the burying-place of Manoah his father
Why is eishet Manoach not mentioned here? Was she still alive? Was she buried elsewhere? Rashi, Radak and Metsudot are all silent on this issue at the verse.