Concerns

Hmm ... not 100% sure, but for example, Apple sells the MagSafe Wallet. That wallet can hold up to three credit cards ... but it is "protected" as per Apple to prevent accidental exposure to magnetic fields.

AFAIK, the newer credit card with "chips" are much less susceptible to magnets vs. the older magnetic stripe cards.

Probably not.

You will find out the next time you try to use that card. But I agree with muguy. In my experience, it’s not been a problem but I try not to make a habit of it.