finding an object in a ray

in my game, you have to find three bombs in order to blow up the enemy base. it works fine, but players seem to have trouble finding the bombs, so now i want to create a function that tells them where the bombs are generally. as of now, i've got my variables, $bomb1, $bomb2, and $bomb3 to determine if they are even on the field, or if they've been picked up. the problem is i dont know how to cast a ray that checks for an item from the player. in the mission, the bombs are called bomb01, bomb02 and bomb03. code would be really helpful