I'm going to assume a couple of things here:
1) You and your reseller don't have direct access to the site's administrative area (maybe your hosting plan expired?).
2) You're using a normal reseller (i.e., lazy).
If your site is just made up of a bunch of static HTML pages and is still accessable via the Web, you can just visit each page on your site and save it to your hard drive. Of course, if you are using any type of server-side scripting (PHP, ASP, JSP, CGI, etc) or if the site is down (as assumed in #1 above) then this won't work.
Most resellers don't consider your lost data their responsibility, so they may or may not be trying really hard to contact the host provider (i.e., they may have sent a couple of emails). If your hosting account has been suspended/deleted, most hosting providers will still have a backup of your data and can supply you with a copy of your site (although there is usually a fee involved of ~$50).
My suggestion is to CALL the hosting provider and explain the situation. Even if they tell you that you need to go through your reseller to resolve this, at least you can tell your reseller that you were able to get in contact with the hosting provider so they shouldn't have any excuse for not doing so themselves.