Theme dropdown in settings is blank

I've been working on a shopping cart for quite some time now. It does have a custom theme and it has been working without a problem. Tonight, I was adjusting the address in System>Settings and when I saved and went to look at the site, I got an error saying "Notice: Error: Could not load template" and it referenced a tpl file that it said was missing. I went into the FTP and into the path it said and saw it was missing, but the path mentioned was default and not my custom theme. So I went into the custom theme and saw the file it said was missing. That's when I came across the issue... I went into the Settings again and to the Store tab and under Template the dropdown is blank. It doesn't even say default anymore. If you click it you just see a blank little box. I've cleared cache, looked on different computers, tried different browsers all without luck.

I'm using Opencart version 1.5.6.4 and the custom theme Margaretha. Everything was working fine and poof no more templates listed. Does anyone have an idea what happened here??