My Bank Charged Me a Fee for an Unauthorized Paypal Transaction

Description

Three days ago, I paid for a product using my PayPal balance. This transaction appears – correctly – in my ‘Activity’ for the day and went to the correct seller. This morning I received an email from my own credit union – which is linked to PayPal for fund transfer, but which I did not use – for having insufficient funds for the very same transaction and amount, and I was charged a $25 penalty fee by them. I do not understand why my credit union was even aware of the PayPal transaction that I made. Has anyone in this community had transactional PayPal glitches of this sort? And should PayPal compensate me for their error? Thank you.