While it is very difficult to answer your question diffinatively without knowing the facts of the case exactly, what you discribe doesn't seem to be too concerning at this point. People claim they are going to sue all the time and this very rarely happens. If your father did not co-sign on any paperwork or have any input on the bail or bond, it is difficult to imagine how this bondsman might allege that your father owes him money.
If the bondsman calls back, I would recomend that you ask him to send you a letter outlining his claim and including any paperwork that he has to support why your father owes him money; either that or refer him to the lawyer of your choice. I would not speak to him about the facts of the matter until you had recieved that information.