I just updated my addon to V1.13.2 and it seems to have broken. I can't access the addon in game to change it back to how it was.

Just had the same issue. The problem happened after he added a second version of the addon.

V1.13.2 is for WoW Classic. The older (previous) version was for the original WoW (V8.2.2).

Go download V8.2.2 and it should fix it.

So I did this, but forgot to lock it.

Is there any plan on splitting the addon in Curse, etc.?

Why would I split the addon?
Twitch automatically selects and installs the correct version so I don't consider there to be a problem here.

Why would I split the addon?
Twitch automatically selects and installs the correct version so I don't consider there to be a problem here.

This has not been my experience. I have classic and retail installed in the same folder (as Blizzard recommends) - i.e.:
c:\World of Warcraft is the install folder when installing both
c:\World of Warcraft_classic_ has the Classic exe and data
c:\World of Warcraft_retail_ has the Retail exe and data.

Twitch multiple times has chosen to upgrade to the 1.13.2 version. The only way to get the proper retail version is to force Twitch - either remove and unzip the addon manually or go to the addon page and manually install a version, and in either case disable auto updates for the addon.

I'm not going to argue that it's a SexyMap-specific problem, but at the very least, Twitch's 'smart' behavior isn't working in all cases.

Twitch's "smart" detection only works if you're on the latest version of Twitch. If you've kept it open all this time instead of restarting it, it won't have updated.