Register your domain as a trademark. It costs a few hundred dollars, and can be done online. This gives you stronger rights with ICANN, against anybody who illicitly acquired the domain, against typosquatters, the registrar, and the courts. You can send intimidating lawyer letters, and quickly escalate from the registrar's support department to lawyer-to-lawyer phone calls. ANIMATS®
I own a domain registrar. Personally (not our official position), I would never try to bring a trademark into this type of dispute. Once you make a trademark claim the domain gets locked to prevent any further changes and you get directed to file a UDRP. We will then act based on the ruling, which could take months. Same for trying to send "intimidating lawyer letters" (or having your attorney contact us at all). Out…
That's fine, you're paying for all lost business revenue during that time since it was obviously caused by your gross negligence (liability for which cannot be waived). Hmm. Might be in your interest to undo the mistake quickly?