That's not what the party publicly stated at the time although they did say they would have preferred the STV, (single transferrable vote). The Lib Dems campaigned strongly for a 'yes' vote in the referendum as did Ed Milliband.
Exactly, they said they would have preferred something else. That sealed the No vote in an instant. Milliband did back the yes vote, but Labour MPs were allowed to campaign as they saw fit and more Labour MPs supported the No campaign than the Yes. It was held on the same day as local elections, including Scottish Parliamentary and Welsh Assembly elections, stopping SNP and Plaid Cymru actively campaigning for a Yes vote. It was a waste of time, Cameron got what he wanted, and Clegg sold his principles down the river.