That's about the way I'd handle it too. I'd toss in an "I'm sorry, I know it's not an acceptable reason for not getting back to you, but I'd really like to have the opportunity to set things right."
There probably is no way to figure it out until you make the call, or set up the face to face appointment. I think your honest regret in not following through will win them over, but I think you're going to have to figure out what to say based on their response.
You got guts...good for you!
Murray