O seguinte funciona para mim:
$ cat test-keystore.sh
#!/bin/bash
keytool -list -keystore "$1" -protected 2>&1 | grep 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 >/dev/null
$ find -name '*.keystore' -exec ~/test-keystore.sh '{}' \; -print
/home/tavianator/android-prod.keystore
Substitua 00:00 ... pelo seu hash real, claro:)