Well, I was convinced that there would be a difference if one mixed each with a little water - surely the bicarb (raising agent) in self raising flour would react with water and give off bubbles of carbon dioxide... but nope.... not a bit of it! I mixed a teaspoon of each type of flour with a tiny bit of water in different glasses and watched and waited.... and waited .... and waited... I even tasted both - the one containing SR flour tasted slightly more *soda-like* to me than the *plain* flour one... but no other obvious indications were present.
Given that both sorts of flour are not that expensive, I'd suggest you start again with fresh flours.... and label them !