I do some part time gunsmithing for friends. I am now working on the 3rd Mossberg 500 that lost its safety button.
If your not familiar with this issue. The 500’s safety button is plastic and likes to snap in half. When this happens the detent ball and spring pop out of the top.
The repair is simple and Brownells has a machined aluminum replacement button available along with all the little parts that go flying out.
BTW, if this happens to you DO NOT LOSE THE SAFETY BLOCK. This is the part that engages the trigger in the receiver. Mossberg will only sell this component to FFL holders.