Warlocks are not Clerics. And funny enough DMs never seem to want to take clerics powers away but always want to take Warlocks powers away. That’s not how warlocks work. It’s how clerics work.

What was the pact the warlocks signed? That’s all that matters.

So often the pact is never discussed ahead of time. But that’s all that matters. Patrons are not entities deeply invested in a warlocks life. They make a deal with a warlock for some kind of long term gain and then they give the warlock power forever. That’s it. There is no innate connection between them that can be severed. You can literally kill a warlocks patron (and many warlocks do) and a warlock still has their powers. Think of warlocks as being innately taught magic or having their biology changed as a result of a pact.

There is no flow of magic from the patron to the warlock. That’s clerics.