Unless something strange is happening with sketchup on your computer then the skb file is likely to have the model as it was before you changed it.

I had a thought of what might have happened so I did a test to see if it does what I thought.
I have backups turned off in sketchup so I turned it back on.
 
I opened a model file and then clicked "save as" and saved it to a different folder. I then went and checked the folders
My original file was still in the original folder as an .skb and the new model was in the new folder as an .skp

So are you sure you saved your modified model to the same location?
It should be somewhere because I find sketchup to be pretty reliable.
Maybe you can open sketchup and reload the modified model from the "recent list" at the bottom of the file menu.
Then choose save as and take note of where it is located.

i7-3770 3.4GHz CPU 16 GB Ram   
GeForce GTX1080 TI 11GB
Windows 10 Pro 64bit

Thanks. I opened it in iClone and it did fine. I thought I had tried that before but, apparently, I hadn't. I'll pay a lot more attention when I'm saving files from now on. Whatever happens I know it's not Sketchup's fault. It's strange that the 3Dexchange thing wouldn't recognize it.

@allamosa: Your descriptions of what you are doing are a bit confusing, as it seems to suggest sometimes that you are opening SKP files in iClone, which is impossible. What I usually do after converting a SKP file in 3DXchange is saving the file first in iClone format (iProp for props). I find that more reliable than sending the converted model directly to iClone.

If you seem to miss elements from your model, you are dealing with what Cricky mentioned, which is that SKP models are often not carefully constructed, such that both front and back faces have part of the visible information. What you can try in those cases is to set the textures of such elements to two-sided. For smaller models, I actually don't bother with hiding the back faces, exactly because of the problems as you describe. 

EDIT: Also, this is the CrazyTalk Animator section of the forum. You may get more effective responses when posting in the iClone section.

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OK, I have been using this section but I will go to the iClone section.  
The files that I saved claim to be SKB files but when I look at the Properties it has it as iproject. The 3Dexchange will not open it but iClone 6 will. I believe that is what happened, I tried opening it in 3Dexchange and since it wouldn't I assumed iClonr6 wouldn't either.