On my birthday I visited my father

bad Russian

Funny enough, it looks like a lot of Russians think it's деньрожденье, whereas it's день рождения.

If only this. One can only guess that it's supposed to mean "в день (моего) рождения".
"НА день рождения" means to go to some other person's burthday party.

Maybe she means "On the day of [someone else's] birthday (party), I was at my dad's."

I think they meant their birthday, but with this Russian, you can't be sure of anything.

Blimey! LL has been a real drag lately!

i think the correct question is у кого вы были на дне рождения.

i think the correct question is у кого вы были на дне рождения.

thanks for all the replies

thanks for all the replies

Whose birthday party were you at?

The question У кого вы были на дне рождения? requires an answer like Я был на дне рождения моего отца.

So my question is correct.

Yes. The answer isn't.)