He made an amulet with Qur’aanic verses for his wife to wear

If an amulet is made with something other than Quran or du’aa’s narrated from the Prophet (peace and blessings of Allah be upon him), or if it contains symbols, mumbo-jumbo and strange words that cannot be understood, then there is scholarly consensus that it is haraam and constitutes shirk. But if the amulet is made with Quran or du’aa’s narrated from the Prophet (peace and blessings of Allah be upon him), then there is a difference of opinion among the salaf, but the correct view is that it is haraam. See question no. 10543. 

The scholars of the Standing Committee said: 

The scholars are agreed that it is haraam to wear amulets if they are made with anything other than Quran, but they differed concerning those that are made with Quran. Some said that it is permissible to wear them and some said that that is not permissible. The view that it is not allowed is more likely to be correct because of the general meaning of the ahaadeeth, and so as to prevent the means that may lead to shirk."(Fatawa al-Lajnah al-Daa’imah, 1/212 )

So you and your wife who asked you for this amulet should remove it straight away and burn it. You said that you did that and you did not know that it was shirk, so you are not to be regarded as a mushrik or a sinner because of this action, since you did not deliberately commit an act of sin.  Allah says (interpretation of the meaning): 

“And there is no sin on you concerning that in which you made a mistake, except in regard to what your hearts deliberately intend” [Al-Ahzaab 33:5] 

“Our Lord! Punish us not if we forget or fall into error” [Al-Baqarah 2:286]

And the Prophet (peace and blessings of Allah be upon him) said: “My ummah is excused for their mistakes, what they forget and what they are forced to do.” 

This evidence indicates that whoever commits a sin but does not know it is a sin, is not to blame, and that Allah has forgiven him. 

And Allah knows best.