Self-custody losses are more often failures of backup than failures of security. The recovery phrase is a complete copy of the wallet, and copies fail in predictable ways.
What the phrase actually represents
The words encode a single large random number from which every address and key in the wallet is derived. Reconstructing that number reconstructs the entire wallet.
Because derivation is deterministic, the phrase is not a hint or a password reset. It is the wallet, and anyone holding it holds equivalent control.
That dual nature creates the core tension in every backup decision. Protection against loss pushes toward more copies, and protection against theft pushes toward fewer.
The storage medium usually fails first
Paper is vulnerable to water, fading ink and the ordinary chaos of moving house. Many phrases are lost during a relocation rather than to any attacker.
Photographs and notes applications are worse, because they sync to cloud accounts that are themselves protected only by a password and a phone number.
Metal backup plates address fire and water but not discovery, since anything durable enough to survive a house fire is also durable enough to survive being found.
Transcription errors surface years later
Word order is part of the data. A phrase copied out of sequence is a different wallet entirely and will restore to an empty balance rather than throwing an error.
Handwriting causes its own trouble, since several words in the standard list differ only in their opening letters and are easy to confuse under pressure.
The list includes a checksum, so many mistakes are caught at restore time. The dangerous errors are the ones that still produce a valid phrase for the wrong wallet.
The optional passphrase surprises people
Many wallets support an extra passphrase that produces a completely separate wallet from the same words. It is sometimes described as a twenty-fifth word.
Forgetting it is fatal in the same way as losing the phrase, and there is no record of it anywhere in the backup unless the owner wrote it separately.
It is also invisible to anyone recovering the wallet later, who will restore the phrase, see the empty default wallet, and reasonably conclude the funds were moved.
Inheritance is the unsolved part
A backup that only its owner can find dies with its owner. Families are left with a device, no phrase and no way to demonstrate the balance ever existed.
Splitting a phrase across trusted people or locations reduces single-point failure but adds coordination problems that surface at the worst possible time.
Anyone arranging this in the United States has estate paperwork to consider as well, and the specifics vary by state and change over time, so professional guidance matters here.