when it's raining I also put my phone in a ziploc bag and would prefer to not have to take it out of the zippered pocket of my grip bag at all unless absolutely necessary, but it does seem like a (preferably new) ziploc bag should be fine for this purpose. I was also just thinking, it might be possible to use a phone that has no mobile data if there is wifi available to upload the scores so maybe that's what I would default to. but otherwise the requirement for a phone is actually not just for a phone but a phone + some sort of plan that includes data. which to a lot of us is no biggie but still in this day and age should not always be assumed people have access to IMO
As of now, you always have the option of paper scorecard.