How did my company found out that I shared confidential information online?

I mistakenly shared configuration file of sth of my company in stackoverflow/reddit. My company found out immediately and fired me. How did they find out? Was it by looking at stackoverflow/reddit? I put them on pastebin and shared. AFAIK, pastebin isn't indexed by google. So,how would they know it? I'm really curious about the infrastructure in companies to figure these stuffs.