Can 財布を無くしました be interpreted as 無くする instead of 無くす?

Question

There's a flashcard from Japanese Level Up for 無くする that I believe has an error:

無くする
どこかで財布を無くしました。

I think the key word should be 無くす and not 無くする, because it's the much more common variant and how most people would interpret the sentence.

But I'm curious if the card is actually wrong.

Is there any possibility for 無くしました in the above sentence to be a conjugated form of 無くする? Or is it only grammatical if the base word is 無くす?

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The 大辞泉 definition for 無くする is as follows:

なく・する【無くする／亡くする】
［動サ変］［文］なく・す［サ変］

１ （無くする）「無くす1」に同じ。「戦争を—・する」「意欲を—・する」
https://dictionary.goo.ne.jp/word/%E7%84%A1%E3%81%8F%E3%81%99%E3%82%8B/

The example sentence「意欲を無くする」implies that 無くする can mean "to lose" in the same way as 無くす.

Answer 1

Modern Japanese speakers should always stick to the godan verb なくす. Unless that flashcard app deals with rare vocabulary that is well beyond the JLPT N1 level, it's safe to consider that information a mistake.

In general, you will never use the verb なくする yourself, although you might see なくする used in old novels or such. In particular, the negative form of this verb is always なくさない, and I think I never heard なくしない at least in conversations. It's true that verbs ending with する/す are sometimes tricky and unstable, but in this specific case, なくす is overwhelmingly predominant.