I had an AT&T iPad 2 3G which I took back to the Apple store on a warranty, and they gave me a replacement one. When I got back (it was an 1.5 hour drive), I realized that I forgot to specify that it's AT&T, not Verizon. Now I know that, chances are, they gave me the correct one, but how do I verify if the iPad is GSM or CDMA-enabled? I don't have a SIM card handy at the moment, so the easiest solution won't work here.
Correct if wrong but I am sure that only the GSM devices have a micro sim card slot. The CDMA or Verizon ones do not have sim cards.
So as you are on AT&T they would have seen a SIM and got you one with a SIM.
It's impossible for them to give you the wrong one even if they tried, the system doesn't allow it.