massive SERPS loss after index.html directory change

Greetings everybody, my website used to rank pretty well ( top 20 ) for most of my keywords. Since I changed my index file's directory I've almost dissapeared from SERPS ( more than 15th results page for the same keywords ) except for searches relative to the domain keywords. I've checked and there is no penalty involved, what could be the problem? Thank you and nice to meet you all.

why did you move it?

When a url is ranking, don't change it.

If you must change it, 301 redirect the old url to the new one.

I didn't want to overwrite the old files so I created a new directory and set the new root directory to my server. There were 3 static pages, the url of the index page stayed the same but the other two that changed the url lost their PR also. Is there anything I could do to fix it, at least get some ranking back..I guess I'm learning the hard way

You need to do a 301 from all the old urls to the new ones. Right now all your existing links are going nowhere and you need to fix that.