#!/bin/bash
who="${1% }" who="${who,,}"
arr=(/var/irclogs/_esoteric/????-??-??.txt)
gawk -vw="$who" -vOFS=":" '
tolower($2) ~ w{x=$0} ENDFILE{if(x){print substr(FILENAME,1,10), x; exit}}
' < <(for ((i=${#arr[@]}-1; i>=0; i-- )); do echo ${arr[i]}; done)