O cache está na memória, não salvo no sistema de arquivos.
De man dnsmasq
:
The cache statistics are also available in the DNS as answers to queries of class CHAOS and type TXT in domain bind. The domain names are cachesize.bind, insertions.bind, evictions.bind, misses.bind, hits.bind, auth.bind and servers.bind. An example command to query this, using the dig utility would be dig +short chaos txt cachesize.bind