I think this is more common than we know.
It is. One of the crimes I investigate is financial fraud and it is pretty common in the banking industry. One case I worked on involved a VP of a bank who received a $200K Commisiion on one mortgage loan he approved that he knew would never be repaid. All the financials, including the tax returns and collateral were a sham.
It happened to my grandparents. They had a CD for a term and didn't tell the bank to convert it or cash it when it reached its term, so they lost it. That is, by the time they checked on it their right to cash it had expired.