Joe Francis' GF to Vivid Honcho Steve Hirsch -- Thanks for Keeping My

Joe Francis and his hot blonde GF can't thank Steve Hirsch enough for snatching their sex tape off the market -- in fact, Joe's GF has even sent the Vivid honcho a thank-you letter, gushing about how Steve kept her private parts ... private.

TMZ has obtained a copy of the letter Abbey Wilson sent to Hirsch. Here's the transcript:

Steve, Joe has always said what a stand up guy you are in business and what a great friend you are. I want to thank you from the bottom of my heart for helping Joe and I out in this unfortunate situation. It's calming to know that we have such a loyal, true friend when an unexpected problem arises. You are a compassionate, warm hearted, and caring man that we are so grateful to have in our lives. Thank you again,
Abbey Wilson

As we reported, a sex tape featuring Wilson and the "Girls Gone Wild" honcho was being shopped to various media outlets. Francis had threatened to sue everyone and their mother over the tape, claiming it was stolen from Wilson's iPad.

When the person selling the tape went to Vivid, Hirsch did Francis a solid and purchased it (for an unknown sum). He then returned the footage to Francis and promised never to release it.

It was an especially big deal for Abbey and Francis ... because neither has ever appeared naked on the Internet (shocking, we know).

Now that's what (porn) friends are for.