Is it a bad sign that they could see a liver mass on ct even without contrast? i have read most are missed when contrast isn't used.

Well defined lesion: If a scan without contrast reveals a liver lesion it means that the lesion is distinct within the liver. The purpose of contrast is to add an agent intravenously that adds detail to the vascularity of the tumor allowing it to be more readily seen. when such a lesion is found and there is no primary noted we do PET/CAT for further enhancement of the liver lesion and look to detect the primary

Yes: This mass can be non cancerous cyst,or can be cancer that has spread to liver as i see that you have thyroid cancer,I hope it is non cancerous,god bless you.

Not necessarily : It is true that you may not see a liver mass without contrast given IV. By the same token there are benign and malignant liver lesions that you can see very well without contrast. Let the radiologist make that call