I am not sure I can give you a good answer for that, but the bad news is that he will probably keep getting stuck in there until you add something to prevent it... My wrasse got trapped in the overflow twice before I added a wad of filter floss. A couple of weeks later he jumped out of the tank and I didnt find him until I moved. Other things you might be able to use would be plastic netting or something to that effect.
Sorry, I hope you can get him out safetly.