Korean Egg Mishap!

I woke up this morning and got prepared to cook some breakfast. I had gone shopping with my roommate yesterday and was looking forward to having some fried eggs. When I had bought the eggs, I had noticed that they were browner than I was used to back in the states, but didn't think too much about it and went those eggs because they were sold in a six pack. Anyways, I heated up some oil and went to crack the eggs. I immediately noticed that they were harder to crack than eggs I was used to. When I finally got one to crack, expecting the nice yellowy substance of an egg yolk dripping out, all I got was a hardened substance that moved about as fast as a cement block! Hmmm...upon further investigation, I peeled the rest of the egg open and discovered a hard boiled egg sitting inside of the shell! What, now how am I going to tell the difference for future shopping trips? Any suggestions? Interesting discovery to say the least.