Highlight Search Results in Scratch Buffer from "Gather" function

I recently installed the "Gather" function described in Vim Tip 1557 at http://vim.wikia.com/wiki/Filter_buffer_on_a_search_result. The function works great, but I would like to apply the original search criteria to the lines in the scratch buffer (with hlsearch on) to highlight the strings found. I tried /a:pattern after the results were appended to the scratch buffer, but that didn't work. How can I do this?
 
Thanks,
Roy Fulbright