Bait the trap with a scrap of composite decking.
Or you can put your favorite shirt in there. They'll want to chew holes in it, just to keep their teeth sharpened.
To make your trap more sensitive, tape or glue some weights atop the metal plate that triggers the trap. (Coins, washers, composite decking scraps).
If a chipmunk couldn't get out, I'm curious how your trap's model was selected.
