Website Hacked with Offensive Link

My website https://www.prologueaviation.com was hacked with a an offensive clickable link on the homepage. I couldn’t locate the source of the link so I disabled all plugins but the problem remained. I took the whole site offline using the “Disable Site” plugin but the link still remains on the offline page. I have no idea what the source of the problem is and how it remains even after the whole site is offline. Note also that the offending link does not show when previewing the site in Dashboard – only when viewed on a browser outside of the WordPress development area.