If your box was full, the default action by the message system may be to delete any new incoming messages until your box received the necessary attention from you. I am just guessing here. That is why they set size limits. Other wise there would have to be message queues for the queues and size limits on the holding boxes for each user... Am I painting a picture that is understandable?
Again, it is just a guess, but I do not think you will see those messages appear in your inbox. If you still have the email notices, you can PM those people who tried to send you a PM and let them know your box was full and you didn't get it.... yadda, yadda, yadda...
I am not on staff here. Just a computer nerd. If there is anything I can do to help you maximize the enjoyment you get from your box, please let me know.