You have to always close a transaction correctly, before relisting , so yes, you did make a mistake.
eBay do allow 2 days fot payment, but most sellers will allow a little longer. You then should open an unpaid item case in the Resolution Centre, and close it 5 days later. Your seller fees are refunded, the buyer gets a non payment strike on their account, they are only allowed one, and only then, are you safe to relist your item.
You must post the item to the buyer who paid. And cancel the item you relisted. Go to the right of the item, from More Actions drop down menu select End item.
