The idiomatic expression "count noses" refers to the act of taking attendance or determining the number of people present in a group. Antonyms for this phrase could include "disperse," "scatter," or "dissipate," indicating a state of dispersion or lack of cohesion in a group. Other possible antonyms might include "shrivel," "diminish," or "shrink," indicating a reduction of numbers or decrease in size. "Lose track," "confuse," or "misplace" could also function as antonyms, suggesting a lack of clarity or organization in accounting for the presence or absence of individuals.