GLOCK's replacement firing pin safety and spring are available for routine maintenence needs. Typically, small parts like this under spring pressure may easily get lost during very detailed disassembly, because of their small size and ability to fly quite far. Fortunately, the replacement parts are inexpensive, and readily available.
Glock Firing Pin Spring 24N Silver SP00063
WARNING: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov