Are you sure you did the polka dot pattern using a standard filter? As R_Kelly says, the square half tone can be done using the filter he mentioned with the Dot option, and contrast set all the way up, but I can't think how to do the polka dots. Could it have been Eelements and not Photoshop?
Easy to do with a pattern fill though. You can download a large number of different dot patterns, or simply make your own.