Is this a loose part of MacBook Pro 2010 (15" version)? Upon opening a MacBook Pro (15" Mid-2010, 2.67 GHz i7, 8GB, GT330, Hi-Res anti-glare display), I noticed a small loose plastic part. Its diameter is ~5mm. 

Does this plastic part belong to the MacBook Pro?

Should this plastic part be attached to something?

Below are pictures taken from two opposing sides, and from the lateral side (object leaned to watchmaker's screwdriver)
In the meantime I found out that this part forms the inner part of the rubber stands at the bottom of the laptop.