Is it wrong?

So my s/o and his mom took my daughter to a dr appointment while I was at work. They brought my daughters ssn and birth certificate. Afterwards, his mother never returned it to us. Well now I’m worried about it. I asked my s/o if he could ask for it back but he’s whatever about it and wouldn’t. And I’m super scared because this lady has a bad history with benefits fraud and I’m scared she will either try to claim my child on her taxes or she will try to get benefits from her ssi or who knows what else (she already tried to do this with her other grandchild and yes the mother is suspicious and upset).

I messaged her some time later on Facebook asking for it back and she said “okay”. So I go over to her house with my s/o that night and she NEVER mentioned it trying to play dumb (I probably should have asked for it).

When I asked my s/o again he said it’s because “she’s afraid we’ll lose it”. Like WOW I’m her mother. Idc if the father or mother has it but we are entitled to it NOT the grandma or grandpa or aunt or uncle.

Next time I see her I will DEFINITELY ask for it but it just bugs me my s/o is so whatever about it despite him complaining she’s controlling over him and shady with money