I'm not sure how to explain what the problem is so I will go with a story:

- I had a working local wordpress installation with a custom child theme. In child theme I had files like `style.css`, `footer.php` or `index.pl` - which I used to place my HTML and CSS. To run it on a server I used command `php -S 127.0.0.1:8000` in my MAC terminal. Everything was working up to this point.
- after committing my work I saw that folder of my child theme is misspelled "tweentyfifteen-child", so I renamed it "twentyfifteen-child" while server was running. This made site not render correctly.

Problem:

- I tried to revert all changes so I renamed folder back to "tweentyfifteen-child", but this didn't help. Main page still was not rendering any of my html.
- when I go to Theme editor I see that files like `footer.php` are not there, only css,
- I even deleted old database and created new one with the same name. Then downloaded clean copy of worpress. And after setting database credentials in config.php and running instalation proccess, I can see Twenty Fifteen Child theme in wordpress cms! even when there is no folder like that in `wp_content/themes`. 

This left me with thinking that when I run `php -S 127.0.0.1:8000` there must be some caching going on... 

Help.