Strange play in yesterday's Cubs game--how was it scored?

During the Cubs’ 10th-inning rally against Toronto yesterday, there was a play I’ve never seen before. Javier Baez struck out swinging on a pitch in the dirt, but he made it to first base because the Toronto catcher failed to throw to first base in time.

Certainly, I’ve seen this happen many times where a batter strikes out but reaches first base on a dropped third strike. What was strange about yesterday’s play was that it was not ruled a wild pitch nor a passed ball. The ball didn’t trickle away that far from the catcher after he failed to catch it. However, he was so focused on preventing the man on third base from scoring, he forgot to throw to first base in time. It was also not ruled an error on the catcher.

How would the official scorer have ruled the play? The box scores aren’t providing much insight. My best guess is fielder’s choice.

Baseball-Reference:

It’s scored as a strike out for the pitcher. Runner reached first on fielder’s choice. Similarly to scoring a fielder’s choice, for example, if there’d been a ground ball to the short stop who’d look the runner back then the throw to first was late.

Thanks! In my OP, fielder’s choice was my guess. I was unable to find the ruling in the play-by-play accounts of the game, though. As Skywatcher said, the accounts just say that Baez struck out but reached first. No other explanation for HOW he reached first.

The OS blew this call. It was originally ruled that Javy reached on a K+FC but was quickly overturned to the correct call, K+WP. Anytime the batter reaches first after striking out, there must be either a WP or PB on the play unless another runner is putout.

http://m.mlb.com/promo/scoring-changes

Cool! The link in Skywatcher’s post also now has the correct ruling of a wild pitch.