Hi @derf123drag - sorry that you're dealing with that!
Buyers are able to respond to a message you've sent for up to 30 days, but if you've blocked them and your buyer requirements are set to not allow blocked buyers from contacting you they won't be able to generate new messages to you (though they are able to 'ask a question' on your items).
I'll review the situation and report the potential buyer for violation if they are breaking our messaging rules. Thanks!
Tyler,