Can apple tell if my iPhone 4s is unlocked by the carrier?

I recently took my iPhone 4s, which was unlocked by the carrier, to the Apple store as it had some microphone issues.

They gave me a replacement iPhone and went home thinking it would be unlocked anyway as it was from the Apple store... once I got home I wanted to make sure it was unlocked so I put in alternative sim card but it told be the sim card wasn't the correct one.

I've tried everything I possibly can to try to get it to work but it just refuses any sim apart from the one that was in my phone when I took it to be replaced.

So basically, my question is, will Apple be able to tell that my phone that I got replaced was unlocked by the carrier? If so will they be able to unlock the new handset or give me an unlocked one?

Thanks guys!