This fell out of my Pioneer SP-SB03. Anyone know what it is?

When I was moving my SP-SB03 sound base I heard something rattling inside. Looking through the ports on the back, I noticed this little wedge thing. After several attempts I was able to tilt the unit so that the thing fell out; it looks like it's made of the same material as the inside of the unit.

Functionality does not seem to have been affected; I'm not noticing any difference in sound quality. I am curious as to what the function of this thing was and whether or not it has any importance going forward. Is it safe to ignore? Will it affect longevity? Any advice would be appreciated.