Can they do something i can't?

Technically it may be possible to know who made the call. But it is unlikely that the threat will be taken too seriously by the authority to do something about it. Get your husband to tell the girl about the threat, and that unless she has other man the husband is the suspect. In any case your husband should lodge a report with his superior so that there is a record. You too should lodge a report with the local police so that they have a record of the threat. Good luck.