This is not a USB stick. USB sticks characteristically have a a male "A plug" which plugs into USB ports, and 2 small holes - read this Radiopaedia article by Dr Matt Bull (famous for naming the manta ray sign): this is what a USB stick looks like:
|Case courtesy of Dr Matthew Bull, Radiopaedia.org, rID: 30286|
The CXR above shows a REVEAL device - an implantable loop recorder device. They are placed subcutaneously and monitor the cardiac rhythm and are used to investigate unexplained fainting episodes to assess for an underlying cardiac rhythm abnormality.