You won't be told who the person was who is ill. But you will be told to self isolate for 14 days.
I can see why they won't tell you.
I can also see that some people (maybe, maybe not - if they are ill, they might not care) - but they could take advantage of this to harm someone.
I would like to know who has listed me as a contact. It could be a mistake on their part.
It's a big ask to self isolate for 2 weeks, especially given the impact on your life, finances etc.
And especially if you don't know who the person is