When the phone was originally sold by an authorized dealer when new, it certainly would have been covered by the standard one year AppleCare warranty. That warranty would have expired after a year.
Since the phone was refurbished, there is no way to know when the phone was originally sold, so there is also no way to know when the warranty expired.
If you had purchased a genuine refurbished phone from an authorized Apple reseller, the phone would have come with a new one year warranty.
Frankly, I am not sure how you can know that the phone really was refurbished by an authorized Apple company, but if the Battery Health was 100% when you bought the phone, at least a new battery was installed.