Money sitting in an old bank account does not simply disappear because the owner stopped checking the balance. If an account remains inactive long enough, the bank may classify it as dormant and eventually transfer the funds to the state under unclaimed-property laws. The exact timeline varies by state and account type, but many states use a period of roughly three to five years.
That creates an odd situation: the bank may no longer hold the money, yet the owner can still have a path to get it back. The state generally holds the property for safekeeping until the rightful owner, or someone legally entitled to act for that owner, claims it. In other words, an abandoned account can become a state-held asset rather than a permanently lost one.