Sounds dodgy to me, but Im not so sure its a debt collector. Buts thats because I assume that they only have the account holder's name, the company the debt is with and the total of the debt, and no other detail.
But if I had gotten that phone call I wouldnt have given out DH's mobile number. I find it strange that she didnt say what company she was calling from and from what you've written was very vague about details. Also normally if you say they are not there, they will give you a number to return the call. There is something dodgy about it though. Hopefully he can give you an answer when he gets home as to what it was about.
A debt collector will have more details than name and address. They would likely have employment history, next of kin, etc because that would be on the credit file. They might not have said where they were from because, due to the Privacy Act, they can't disclose the debt to a third party. That would include a spouse.