They can claim that they were operating on the best information they had, which was probably a list generated more than a week prior if he is in custody in the same state/county? If so, they may be liable for an illegal entry for failure to observe due dilligence in verifying the probationee was not already picked up.
If the officers were not informed that your boyfriend was in custody, it's unlikely you have an argument that they acted unlawfully. If he had been in custody for a significant amount of time (definitely longer than a week) you might have a better position. Sorry.