It is common to have resellers going missing and registrants loss access to the Auth Code. Check your domain whois (
www.who.is) to find out who is your registrar for your domain. Contact them directly, because they are the one actually managing your domain name, not the reseller. You will need to prove that you own the domain name, best if you have supporting documents from the reseller like Invoice. It would be easier if the domain Whois info email show your email address, which the registrar can send the authcode to the original email shown in the WHOIS record. If your email is difference from the WHOIS record, it will take more verification. Hope this help. if you need help to access to the right people in the registrar, you may want to PM me. I think I may be able to help.