You may search for the phrase under Languages & Phrases > Search for Phrases. Make sure to search for the phrase name, not phrase text.
Did you remove it every place it was in the template? It's in there a few times. You might also want to remove this line:
<a href="{vb:url {vb:raw topic.routeid}, {vb:raw topic}, {vb:raw qs}}" class="go-to-last-post" title="{vb

hrase 'go_to_last_post'}"> </a>