It's actually quite simple. Run the following commands.
sudo nano /etc/xdg/autostart/nm-applet.desktop
Find the following line.
Change it to the following instead.
Then save, and restart. That's it!
Sorry the late response. I eneded up restoring an image from a few days prior. I tried several things, but I am pretty good about backing up, so decided to go with that option. I used Clonezilla, so just reimaged the drive and went forward from there.
Some guy on elementary subreddit helped me. There is a bug discussed on github: https://github.com/elementary/wingpanel-indicator-keyboard/issues/80
As suggested, I've changed org.gnome.desktop.input-sources from [('ibus', 'us'), ('xkb', 'ru')] to [('xkb', 'us'), ('xkb', 'ru')] with the dconf-editor GUI tool, and the indicator is visible now.