Sadly there can be pretty immoral people in the world, including a lack of business ethics. It seems an SEO company and their client got in a disagreement about a work contract and the client wanted to part ways. The SEO company allegedly decided to completely sabotage the company in Google Search.
A Google Webmaster Help thread has the complaint from the client. Saying that he told the SEO company that he "was looking at discontinuing service with them." An hour later the SEO company gained ownership status of the business's Google My Business listing and was marked as permanently closed. Then shortly later the web site was also removed from Google using the Google Search Console emergency removal feature.
A Google product expert confirmed that "it looks like they have removed your site from search using Google Search Console. This is a feature that is designed for emergency use to remove a site, page or directory from search almost immediately." But he added that the "good news, it is just as quickly reversible."
A lot of folks gave this guy advice in the thread and it seems the owner was able to lock out the SEO company from the site, and the Google tools.
But this stuff has happened too often. We've seen attempts to hold SEO clients hostage before through SEO threats. Google said when it comes to negative SEO you can ignore it but this is beyond negative SEO, this case above was direct access to remove the site and business from Google Search.
So just be careful when you hire an SEO company. They literally can cause so much damage and you need to make sure to trust them before you hand them over such access to your business.
Forum discussion at Google Webmaster Help.