I get fake service dogs all the time in my Starbucks. I can't kick them out even if they're not in a vest if the owner says they're a service dog. Last week, one of them peed all over my floor, ate a pastry out of another customer's hand, and nearly bit an infant. All in five minutes. Clearly, not a service dog but I still couldn't kick them out to the patio.
Actually, you can. I’m on mobile so I can’t link but look up the ADA.gov FAQ. You are legally allowed to remove any service animal (even legitimate ones) if they are out of control or not acting appropriately. Peeing in a food service establishment definitely counts.
Starbucks may have different rules but you’re well within rights. That’s such a major health code violation…