About a month ago I 301 redirected my forum's home page from /forum/ to /forum/index.php, because the pages were duplicates. Funny thing is, the old page is still showing in Google search results, but the new page was indexed in Google mobile results the first week. Both pages have a lot of high quality backlinks, the new page is listed in the site's navigation and the site has been crawled several times. I'm not quite sure what to make of this. Does anyone have any idea what could be causing this and is there a way to get Google to recognize & index the new page?