i lost my trusted device and its got an activation lock. now i found it but i cant receive verification codes because the number is no longer any good. i need help

My son created two apple IDs both have the same number but he lost his phone. i disconnected the phone number but now he has his device. it was his trusted device and number. is there a way to go around this? i have him as a friend in find my iphone but i cant locate the phone because its been wipped clean? any suggestions on how to get back in it?