IPA: /ʌnˈfaʊnd/
KK: /ʌnˈfaʊnd/
Not discovered or located; something that cannot be found.
The missing keys were unfound despite searching everywhere.
Unfound → It is formed from "un-" (meaning not) and "found" (from Old English "fundian", meaning to find). The word "unfound" means not found or not discovered.
Think of 'not' ('un-') being added to 'found' — this helps you remember that 'unfound' means something that has not been found.