Kid's Apple ID: Unknown number, unreachable trusted device

kids apple id account connected to unknown phone number, trusted device unreachable

State is as follows:

New phone, where she wants to set up her apple account.

Old iphone used few years back, broken and unrepairable (that one is listed as trusted device, so no way to rely on trusted device).

At login, we are asked to confirm the phone number with *** *****05 prompt - but noone in family nor friends have that phone number.

Any of the buttons like "device not available" or similar not possible - it asks simply for the phone number (that we have no idea what it is). The only thing it asks for is to confirm phone number.

I have my apple id, can login, and it's connected to hers as Family - she is listed as my child.

I have checked a lot of similar posts and I haven't found anywhere similar situation...

Is this recoverable?