Your acquaintance is not correct in their understanding of what an SR-22 is. An SR-22 is not actually an insurance policy but a form or certificate showing that a person has fulfilled their financial responsibility. An SR22 is typically required by the court or DMV after certain traffic infractions or if a person was in an accident without insurance coverage, so not a type of insurance you would want to have to carry.
Each state has their own guidelines for a SR-22; some do not require them at all. For Rhode Island, future proof of insurance certificates (SR22) are required in cases of driver license suspension as a result of major conviction or a number of convictions. A policy of liability insurance certified by a future proof filing is not considered to provide absolute coverage.
There are policies available to drivers who do not own cars called a non-owners policy. Non-owner policies though typically are only for liability coverage and do not cover vehicles that are owned by family member or other members of the household.
Normally if you live in a household, even if you are not the registered owner of a vehicle but drive it, you should be on the insurance policy for the vehicle. We are unaware of any policy that would fall under the description your friend gave to you.
You may try checking with the Rhode Island Insurance Division of the Department of Business Regulation to see if any such type of insurance as was described to you does exist in RI.