If you have a sudo ALL capable user account that doesn’t use 2FA you may be able to login with it (any sudo users with ALL capabilities can login to Webmin and they’ll be root, unless that’s been disabled or the specific user has been restricted).
Otherwise, it sounds like your system is pretty secure. Nobody can login at all. 
2FA can be disabled from the command line, but if you can’t ssh, you don’t have that option.
If it’s colocated, most facilities have the ability to hook up a KVM for you (one that can be accessed over the internet). They’re mostly awful Java applets and a pain in the ass to get working, but, better than a several hour drive, probably.
Good luck.