Facebook Question please?

Okay, so Ive been sending messages to someone i am not friends with on facebook. I send these messages by first clicking the 'message' icon on the top right corner of the person's page. Ive clicked it and typed something and clicked sent but i dont know if they have received it because all that appears are what i have written. The 'message' icon on that person's page is still there so does that mean they still haven't blocked me from sending them messages. And if they have, would the 'message' icon disappear? If it doesn't would that mean i can keep sending them messages and theyll keep getting these messages?