menettynyt
Menettynyt is not a standard Finnish word and is not listed in major Finnish dictionaries. It is generally regarded as a nonstandard form and may occur only as a misspelling, a dialectal variant in rare cases, or a deliberate stylistic choice in creative writing. In formal language, this form would typically be considered incorrect.
In standard Finnish, related participles come from the verb menettää (to lose). The past active participle is
If encountered in ordinary text, "menettynyt" is most often a mistake or an attempt at stylistic variation