Carrier outage?

One of our voice conferencing vendors had an significant outage last week, and pinned the blame on a "major US carrier outage" that affected telco resources "throughout the United States". Any way to independently corroborate this claim? I would imagine news of such a major carrier outage would have reached this or another operator's group (and I didn't see anything on this list about one). I'm not saying they're "lying", but I like to check out such claims to ensure my vendors are being honest and up front and not trying to pass the buck. Naturally the vendor did not say _which_ carrier had the outage. Any info or guidance as to where I should be looking for info? Many thanks, Doug