Ask a Lawyer and Get Answers to Your Legal Questions
I am very sorry to learn of this situation.
The other dog's owner is liable for the actions of their canine (whether it was a "real" service dog or a "fake" one - so this is not a defense if they even tried to use it).
You can make a report to law enforcement, they should deal with a dog like this.
You can also file a lawsuit against the dog's owner to receive monetary compensation from the owner. You can sue for up to $10,000.00 in small claims without needing a lawyer. See: https://www.depts.ttu.edu/sls/forms/How-to-Sue-in-Small-Claims-Court.pdf. Your damages include both the cost of the veterinary bills, but also the cost of replacing your service animal.
(I do know how much it costs to replace a service dog, and that $10 grand is probably short, but if you need to sue for more than this it will put you in general civil court, this is a little more complex procedurally so I do recommend that you at least speak with a lawyer for a consultation prior to filing suit - you can still represent yourself, but it takes a bit more work).
You will want to speak with a civil litigation attorney.
You can find local attorneys using the State and local Bar Association directories, or private directories such as www.AVVO.com; www.FindLaw.com; or www.Martindale.com (I personally find www.AVVO.com to be the most user friendly).
I am sorry that the information was not very helpful. I have provided you with the proper remedies (both reporting the matter to law enforcement and filing a civil suit. One to deal with the dog and punish the owner criminally, and the second one to compensate you for the loss).
If you have further questions I would be happy to answer them for you.