Can you be arrested on a 6-month old warrant if there is no charge?

Relative was arrested for DWI 7 months ago when he was affected by heat/dehydration/fever and losing control of driving. He was released instead of being arraigned. No illegal drugs or alcohol involved and he was tested at ER before being jailed. At a traffic stop recently he was arrested on a 6-month old warrant for DWI. We assume it is one and the same. The bondsman and first paralegal we talked to cannot find a charge in the system, only the warrant. Is this possible? Is this lack of due process or some other goof-up? Cost for bond, breathalyzer device for car while on bond, and getting attorney is big concern, much less reputation and missing work. If this is a snafu by the police/city, can the costs be recovered?