Hi Scent,
Happy Father's Day to your husband from me, also. Both responses above are so great. I love the drum set idea and I hope Tish's words brought a smile to your face.
Recovering nailed it.....why are YOU feeling guilty? You tried and your difficult child knew exactly what to say in just a few short words. (and, absolutely, it is exactly like what my difficult child would do).
Are you and husband doing anything fun today? I sure hope so! I hope the weather is beautiful and you take a nice drive for ice cream or going to a movie if the weather is not beautiful.
Why do we give Hallmark or television or any other outside fluff that has nothing to do with our relationships whatsoever, the power to make us sad or resentful or add anything to how we are coping/moving forward? I know I do, but YOU need to stop! 
husband and i went out for dinner last night and he asked, Do you think I'll hear from gfg33 tomorrow? I was taken aback. It has been months and it would be the first Hallmark Day we would have heard from him. But, you know.....i can see gfg33 using today as a way to turn the knife.....thinking, Aha, they will THINK it is a Father's Day message. This will definitely get their attention. Now, they'll get how really through with them I am. (hoping we would grovel and apologize for not sending him $$).
I feel much stronger today, thanks to responses from Tish and Recovering to you. Please, please have a great rest of the day and report back. You are such a source of wisdom for us.