They do mention it. It gets raised at the highest ambassadorial levels a few episodes later in ENT: Shadows of P'Jem when the Vulcan High Command use it as an excuse to recall T'Pol:
SOVAL: The loss to the Vulcan people is incalculable. P'Jem was one of our most revered sanctuaries.
FORREST: Ambassador, we are very sorry for your loss, but with all due respect the High Command has to take some responsibility. You
were using the monastery as a surveillance station.
SOVAL: We were observing a dangerous and aggressive neighbour. The Andorians wouldn't have found the station if your people hadn't
interfered. They've been in space for six months and they've already
destabilised an entire sector.
FORREST: I'm afraid I can't agree with that, Ambassador. This was a volatile situation long before Starfleet got involved. Perhaps if
you'd been a little more open with us, this tragedy might have been
As to why they put the listening station under the Monastery, the answer is that it was a convenient location with a legitimate excuse for regular visits from offworld and that the Vulcans are massively complacent about their ability to avoid detection.