Completely hypothetical (for now, at least

Are there any famous cases of such a thing happening?
Monex will have 1% points from January, if you can get Shinsei to deliver your credit card that is
https://go.sbisec.co.jp/lp/lp_sbi_v_series.html
This is the topic I mainly had in mind when I wrote the post. I wouldn't know where to start, or even who to contact. For stocks, would it be the company whose stock it is? And for ETFs / Mutual Funds, the company whose financial product it is?Your investments are held in your name. e.g. Shares or Mutual Fund units you hold.
I suspect there would need to be a process to move those to another brokerage.