It's about Qo'clock, what time do you have?
The intelligence agencies spy on people all the time without FISA warrants, the information didn't need to be unmasked to know who the collection was against. They had the UK do it to have some level of deniability in case anyone ever found out. The FISA warrant just allowed them to share that information unmasked.
The traitors underestimated the resolve of the patriots amongst them. One of the first tiimes they have been caught in a conspiracy that can truly be traced all the way back to the start.