New iPhone: Almost No Old Photos in Photostream

Question

Hey everyone,
So I recently switched from AT&T to Verizon, and traded in my old 4S for a 5C. I was told to make sure that I backed up my iphone before I switched, and once I did, I gave the representative my old phone and was handed the new one.
When setting up the new phone, I logged into my iCloud account. I did this all at the Verizon store - not connected to a computer. Once the setup was complete, I had all of my contacts, notes, and reminders. All of my existing text messages were gone (although I am sure that is normal because those are not backed up to iCloud I don't think). However, when going to the Photos app, I noticed something strange. Obviously, my camera roll was empty. Under the albums tab, I also had a "My Photo Stream" album. Inside, there were 26 photos. Before I turned in my phone (in the store), I looked and saw close to 1000 pictures in my photo stream.
This happened a few days over a month ago. The earliest of those photos was taken around 1 month before that. After doing some research, I read that the photo stream holds photos up to 30 days. My question is, how come only 26 photos out of the ~1000 were kept? They have been there for around 2 months now.
I'm not too sure if this is important to note, but when I click on the "Shared" tab in the Photos app, it has a button to "Create New Stream".
Do I have to restore my phone from the last backup of my old AT&T 4S? I'm not sure if the representative actually restored it from that iCloud backup: the only thing that was done was me signing in to my iCloud account during the initial phone setup process when not connected to a computer or anything (the process includes language setting, etc.). Also, if I do have to restore my phone, what will get deleted from my new phone that has been added in the past month? I have taken photos, written notes, bought an app, and set reminders.
Thanks in advance! I have been putting this on the backburner for the past month, but I really want to try to figure this out. I look forward to hearing what you all have to say!

Answer 1

Photo stream photos only remain in iCloud for 30 days.  When you reconnected to your photo stream you would only receive the photos from the last 30 days as older photos are no longer in iCloud.  The backup includes camera roll photos (not photo stream photos), and restoring the backup should recover them.  If you only want to recover the photos and not lose the other data on your phone now, back up your phone to your computer using iTunes.  Then restore the backup of your old phone, transfer the recovered photos to your computer (iOS: Import personal photos and videos from iOS devices to your computer), then restore the iTunes backup to get your current data back.