Quoting ♫ boobook ♫:" If he goes pee on the potty consistently I would take the diaper away and just do trainer underwear or ... [snip!] ... in the bed and pee. If he's solo it might be comforting to pee in his bed like at night, I don't think it's weird. He's only 3."
They're home is set up to where the kids room has 2 doors that are always open, one that opens right into the living room and another down by the laundry room. She's always near, he can and he will come find her when he needs to go most of the time.. Just every now and then he'll go in his bed. It just started recently, too.
I'll talk with her about maybe trying some trainer diapers or underwear for him, maybe that would help.