Does the lockdown mode prevent certain contacts from reaching me?

Hello

I received a notification saying one of my contacts tried to reach me, but lockdown mode prevented it.

This is strange because I’m currently texting her, and she says she didn’t try to call. When I click on the notification, nothing happens. Can someone explain how this is possible and why lockdown mode blocks certain calls? Also, could iOS be wrong in saying that someone tried to reach me?

thx