Hi Beverly ! Welcome to the forum and the world of Hibiscus !
Well from what you described is normal for hibiscus. One should not leave them out in frost type temps. Generally tropical hibiscus can not with stand weather below 40 degrees. They will drop all leaves and go into shock.
My suggestion is to get it out the rain ( especially since it barely has any leaves.) rule of thumb I go by is less leaves = less water and longer it will take plant to suck up out of the soil. If you over water hibiscus with few leaves they will throw a fit and drop leaves(They turn yellow first then fall off).
If you say the temperature is right where you live, over watering it could be the problem or spider mites but typically they don't like cold weather. Only water when soil gets dry ( but don't let it get so dry you see leaves wilting )
I hope this helps