I'm sure his FF is celebrating in some way!
Agreeing with so many others, esp. Barb & John. I highly recommend celebrating this day at your house even though he's not home. For Jorge's we had a cake and sang to him and filmed it. We also went to build-a-bear with DD that day and made him a special friend. We have a bit of a tradition in our house of recapping past birthdays on the next one and for Jorge we'll at least be able to show him we had a party and were thinking of him and celebrating his life.
We also felt like it was nice that he could celebrate his 1 year birthday with his FF who had spent that year with him. I know it would be great to have him in your arms on this day, but like others we felt like it was good for him and them to have that day together. It's frustrating and awful that this process wasn't done 6 months ago and it wasn't even an option for him to be there for his birthday and I'm not saying you have to feel that way at all, but I guess as long as you're in this spot it may help to put some silver linings on it.
Funny enough, we had our birthday party here for him and had a chocolate cake with white frosting with blue lettering and strawberries. When we got his birthday photos from the FF (oh yes, there was a big party: pinata, cake, party hats, the works) his cake there was nearly identical.
I'm sure he's having a great day; hopefully you can, too.