Next SLOWLY pry the case back up using the slot. DO NOT rest the ifixit pry tool on the case to pry upwards as it may break the case. The case back will fly off and the small speaker spring will disappear forever if you use too much force. Trust me. You do not want to use the thump method for trying to find this very tiny spring.

The spring is usually held in place with a small extension to the end of the spring and will not normally fall out. If this is not the original spring or it has been improperly inserted it may disappear- make note of this.