I've been denied entry to a couple of countries, and they usually write/stamp something that indicates a reason.
For example, the last time it happened I was returning to the country I lived after a visa trip and as usual was not carrying a ticket to leave the country as I tended to buy round trip tickets out and back and had never had any problems. They stamped my passport "entry denied" when I argued my case (seriously, at this country they never ever
bothered with this rule other than this day and the guy was just giving me a hard time) and wrote in my passport that I was denied entry because I wasn't carrying a return ticket and enough cash. I had to go buy a ticket and withdraw the cash from an atm before they'd let me back in and in many such cases it doesn't mean much more than that.
You said they wrote something in the "back pages" of your passport, well what did they write? It might hint at the reasons.