You removed the drop-down userlist select, but didn't do so properly. This results in Listid being missing from the POST so it will always POST to the default userlist. In other words when you search you're not searching the userlist you were just viewing.
The easiest and safest approach is to just hide it with CSS so its HTML still works. Alternatively you can remove it properly by reviewing my below post.
www.joomlapolis.com/forum/153-professional-member-support/170122-lists-in-separate-menus#170862