[Plugin: Buddypress] Search for custom post type only is not working

I’m trying to show search results only for a specific custom post type, my code is simple and I already tested it successfully on some wordpress sites I made, but in this case (buddypress) looks like it is not working.

Here is my form:

<form id="vendor-search" action="<?php bloginfo('siteurl'); ?>" method="get">
<h5>Search for vendors</h5>
<input type="hidden" name="post_type" value="vendors" />
<label for="s" class="screen-reader-text">Search for:</label>
<input type="text" id="s" size="23" name="s" value="" />
<input type="submit" value="Search" id="searchsubmit" />

So I set this hidden input:

<input type="hidden" name="post_type" value="vendors" />

and then I get a correct URL when searching, something like:
mywebsite.com/?post_type=vendors&s=Marketing
but on displayed results it is including all kind of posts and pages…

Any ideas about what can this be?

Thanks a lot!