Lost contacts after updating on another device

I updated to a new iPhone and gave my Dad my old one. He only really uses it to make calls so I just used my Mum's Apple ID when I set it up, to save me making him a whole new account that he probably wouldn't use. The only problem is that then when I added all of his contacts into the phone, it wiped all the contacts from my Mum's iPhone and iPad and replaced them with his.

Is there any way to get Mum's contacts back?

Please help!

:)