I think it's more a case of "I forgot to renew the domain and someone jumped in and re-registered it" rather than "My site has been hijacked"
This has happened in the past: http://www.out-law.com/page-4049
This has happened in the past: http://www.out-law.com/page-4049
http://www.icann.org/en/resources/registrars/accreditation/e...
Skulduggery Afoot!