Is there a default ID you get for iCloud?

My phone wasn’t working, so I had to go to an apple store. They did some stuff, and now my phone is working, but I lost a bunch of old photos and contacts. I did back up everything before going into the fixing process.

I have 3 apple logins. One is for the US App Store. One is for my native country App Store.

Third one is a iCloud ID that I don’t remember ever setting up. It just popped up on the phone when iCloud was first around. 

I tried logging in to both apple ids. Didn’t get the photos back. I want to try logging into my iCloud ID , but have no idea what it is. Is there any way to find this out? Is there like a default setting what my iCloud id initially is? 

I faintly remember it being something with my name, but I really can’t find out. 

Please help. I really am desperate for all the photos.

Thank you!