My Mom Stole My Boyfriend's Birth Certificate

Location: Wisconsin

(Edited for grammar. I'm on my phone and was rage typing)

My bf moved in awhile ago, like going on 2 years. When he moved in he put his birth certificate into a "safety box" of mine. Its a fire proof box that I left the keys near by because the point was to keep the documents protected, not locked up. Not to mention it was in a part of my house that a theif normally wouldnt look.

Ive been rocky with my mom for about a year. I think shes in the midst of a midlife crisis or something.

Last week my bf went in my lock box to grab the title of his car he was selling, and realized his birth certificate wasnt in there. He asked me and I told him that it was news to me. The last I saw it was when we put it in there.

I talked to my sister the other day and she said she had heard awhile ago mom mention taking it. I called my mom out and at first she was insistent she didnt have it. I googled and found that it can be jail time and fine for having someone else's birth certificate. Now shes insistent that its not a big deal cuz she wasnt using it to get legal documents. If its just in her possession she must have accidentally grabbed it (literaly impossible). She also insists theres nothing cops could do. But then she also claims to not have it and I'm in the wrong for accusing her. Then she goes back to saying she doesnt have it and I'm just stirring the pot.

Is she right? Is it only illegal to have someone else's birth certificate if youre using it? Is it fine to have it just to have it as long as youre not using it?