The problem is that this "back to top" button is appearing despite I UNINSTALLED AND DELETED each and every K2 file and folder (so theres no such item.php because that there is no com_K2 folder). I am suspicious that the code that defines "Back to Top" button must be written in the installation process (before i unistalled the K2) into another code file (maybe into another module's codes I don't know) and i can not find this specific code in my database.
Simon Wells (K2 Support) said:

In the item.php, right at the very end

<div class="itemBackToTop"> <a class="k2Anchor" href="<?php echo $this->item->link; ?>#startOfPageId<?php echo JRequest::getInt('id'); ?>"><?php echo JText::_("back to top"); ?></a> </div> <div class="clr"></div>


Remove that code.

Take note, if you do this in the component template, then update-install K2, you will loose the changes.

Consider using a K2 template over ride, check out my guides on simon.getk2.org 

 

Simon

K2joom

Any other suggestion?

If you have removed k2 and all its directories and are not using a k2 item or category to display content, it must be in your template somewhere....

Well thats exactly what the situation is. My question till the beginning was that i can not find that code (although i searched each and every folder) but it is obvious that it is somewhere in my template. It is a K2 related problem and I just wanted to ask it in this community...

I appended my template's CSS to hide 'Back to Top'

/* Added the following code to hide 'Back to Top' */
div.itemBackToTop {
display:none;
}