I am curious to know what you intend to use such a large flash drive for. You do realize that flash media is the least reliable of any modern storage media.
Additionally, you should always maintain at least two copies of any data you want to keep. All forms of storage will fail sooner or later.
In your case ;you must have improperly removed that drive in order for the format to read RAW.
Always use the safely remove icon in the tray by the clock. If it is hidden, unhide it.