Well as it stands not all steel instruments are protected against rust and more instruments are being made from untreated shells.
Not the end of the world… you should know rust on steel is normal and will not affect your sound instantly – like you have a good week after you see some on your pan to remove it.
Her is a good video on how you can and should maintain your hanpan.
Make sure to follow you handpan makers instruction on the subject. Some instruments don’t need regular rust prevention maintenance as such with nitrated shells, stainless steel or cooper/brass … Tow methods are commonly used other wise :
Oil : this treatment will evaporate or rub off, just add a bit of oil to keep rust away.
Beeswax : this is the next best thing to a permanent coating, just add a bit of beewax base past to keep rust away