“Is there a statute of limitations for filing a patent lawsuit for stolen invention that was already issued as a patent? If yes, then when does this statute of limitations begin?”
If you are talking about a statute of limitations on patent infringement, then the general answer is that while there is no overall statute of limitations, there *is* a limitation on when you can recover damages (i.e. get money), and that limit is 6 years. Generally, most statutes of limitation start running from when the injured party knew – *or should have known* – about the damaging act. That said, we are not intellectual property attorneys, and if you feel that a patent that you own has been infringed on, you should consult with an IP attorney as soon as possible.