The last time a State didn't use a vote was in the election of 1876 when Colorado was admitted as a State too late as to prepare for a vote in the Presidential election. There's no reason to think the result would've been different in that case and it's doubtful we'll see a State ever have the legislature elect the Electors save in a similar situation.
Unless the outcome of an election was in dispute and this hadn't been resolved by the time te EC was due to meet. I could imagine the Legislature then stepping in to ensure that the state wasn't prevented from casting its EVs.
