Explain all of that to them. They may absorb the $20 hit for you. Same thing happened to me. A few years back, $150.00 charge back, I called PP, explained the situation, explained my business with them, how I'm an existing long time customer of PayPal. They forwarded the complaint to a higher up, 3 days later, they absorbed the the loss and thanked me for my business.
However, with that being said, in the event they don't. You can remove your credentials off the account and let it go stale. You will not be able to use those same credentials on a new account though. If you create a new PayPal with that banking account or credit card, it will likely link those 2 accounts together and cause some issues.
They also send a couple emails threatening you with creditors down the line. However, I can't imagine they'd go after you for $20. Alas, I digress, give them a call, explain yourself, sound upset. Should be fine.