Imagine instead of seeing your web site address, i.e. domain.com listed in the Google search results for your brand name, instead you see an IP address listed. I am sure some of you have stumbled across this in the past, either with client work or just normal daily searching. But it can be a scary thing to see Google listing the IP address of your site over your domain name.
Google's John Mueller said on Twitter that "either way, this doesn't hurt rankings" to have your IP shown instead of your domain name.
Let me share the context:
If you're checking with a site:-query, you're probably seeing URLs that already switched back. Either way, this doesn't hurt rankings.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) November 20, 2017
So Google started picking up the IP because of a technical issue on the webmasters part. But now, the webmaster is probably using a site command to see if the IP address results still come up. If they do, that is probably normal. If the IP address comes up for a normal query that your site would rank for, I'd be upset.
Either way, over time, Google should pick up the change and the IP should stop showing for normal queries. The site command may continue to show it.
In terms of it hurting - well, if people link to your IP over your domain - that is not a great thing. You want people to link to the specific URLs you want to rank well, not to the IP addresses. Google can probably canonicalize the IP to the domain correctly but in terms of links, that can get a little sticky.
Forum discussion at Twitter.