I also have the Z10 and there is no option to save a photo if you are using the Facebook app. I have work around and I use the built-in web browser.
1. Open the image.
2. Choose "View Full Size".
3. Long press on the image.
4. Options appear on the right side of the screen.
5. Tap on the black button. The one encircled below. I do not know what it is called. LOL.
6. Save the image.
Hope this helps.
I just updated the FB app. Saving the photo is available using the app. Open the image. Press and hold the picture. An option shows up on the right side of the screen. Save it.
Additional info about the facebook app.
The maximum pictures you can upload on a certain album while using the MOBILE FACEBOOK APP is 100 pictures. If happens that you can't upload more you can create a new album then upload it on that.
Facebook® has a limit of 200 photos per album. The Mobile album has a limit of 100 photos. It is possible that the album being chosen for upload is full.
Hope this helps,