In 2015 when we hosted the regionals, I remember #1 Minnesota State going down to RIT in the first round. What I can't remember if RIT was the 16th seed, or if that was switched around for some reason
I thought North Dakota was the overall number 1 that year though. But you might be right to question it, because it may have been MSU, which would mean that year the overall 1 lost to the overall 16.
I remember Minnesota State was the official #1 seed based on Pairwise.
I don't remember who the polls had as #1, as it's always tough to compare teams (either objectively or subjectively) from the NCHC and the WCHA.