need help...thank yous, back ordered gifts and registry

Ok....a number of my gifts are on back order, do I send notes now, or wait until they arrive?
I feel rude, but the thank you is sort of a confirmation the gift arrived, right?
Also I can not tell from the registry the difference between somebody who bought a gift and is holding it to give me in person, and someone who is shipping it.
To make matters worse, Bloomingdales had a system problem with their 'thank you note' list, so they say the registry may be incomplete.

I wanted to finish my notes this weekend...ugh!

thanks for the advice. I've made a mess of it...I had all the gifts shipped to my husbands place, we are not moving in 'till October so they have not been opened.

I'm gonna have to do some guesswork.