Just to clarify OP did a return on his fold 4... not his trade-in deviceThey didn't ask me for the IMEI number before shipping. Most people don't have their IMEI number either. You might be able to get it from the carrier but if it's already on someone's account they can't block it. So I suppose they could, but they won't put that kind of work into it, the person that owned it would have to do it.
And chances are if it was stolen is probably leaving the country and I think they can change the IMEI number also. That I'm not sure on