My mom put a package of Wilton cake fondant in the freezer by mistake. Will it still usable once thawed and, would you thaw it now or just before its intended use?
Yes, freezing fondant is fine if it is well wrapped, although doing so is not normally necessary as it is so high in sugar that it is essentially shelf stable.
The main issue is that when you thaw it, you want it to be well wrapped so that condensation does not get onto the surface of the fondant itself, making it sticky.
This link should help. One of the replies says that if you do freeze your fondant, you have to bring it out of its frozen state by refrigerating before bringing to room temperature to finally dry it out to its normal consistency.