Sarah, that was a wonderful thing you did for Wyatt. And I agree with you that the hardest thing is parting with a beloved dog even when you know it's going to an excellent home. Your head knows that this is the most wonderful thing for the dog but your heart aches because the bond is so strong.
I thought Phred's advice was excellent about a 'substitute'. Could I also suggest you have a couple of excellent photos of Wyatt...one with his great new family. Look at those photos as much as you like & your heart will sing when you see the joy on all their faces. Keep a picture of Wyatt in your wallet...& show him to people as your very favourite foster-dog who is now living in a Doggy Heaven on Earth. Watch the joy on dog lovers faces...because this is what we would want for EVERY dog. And Wyatt got there because of YOU.