Any proper website would list ways to contact them, especially if the main purpose is listing things. Not just that, the site itself looks pretty outdated, it feels like it's unfinished and neglected, it doesn't do well on SEO either, there's probably only a few who uses this, or maybe no one(?).
I don't think you should worry too much, If I were you, I would focus on the most used sites like coinatmradar.com. But if you're really serious about this, I guess you can try sending an email to "
cryptocurrencyatmlocator.com@domainsbyproxy.com". Do note that since their whois data is private, it's just a proxy email managed by a third party based on the owners' set preferences, so if they chose not to forward any emails, the won't receive yours.