2FA wouldn't come into play at all,
your bigger issues would be water damage to the tag itself, and possible complete loss of cell service, meaning tags locations wouldn't update, since there no way for the other apple devices to send the updated location.
as long as the tag is still in working order, and your phone has a charge, you can use the precise location feature, even without cell service or an internet connection. The only limitation is you need to be fairly close to use the feature. As long as your house isn't too far from where it used to be, you should be able to find your things.
the only time you'd have to worry about 2FA is if you needed to re-log into your phone, which you should only need to do if you've just got a new phone. and in theory, if there is enough infrastructure to purchase a new phone, there should be enough to get your 2FA code.