Volume button retaining clip magnets

In the store ifixit sell VBRCs (seen here). When I repaired an iPhone 7 plus where the lower volume button remained depressed without popping back out, I came across these. Inside the phone there seems to be an ever so tiny magnetic disk sitting in between the “smile” and “third eye” of the VBRC. It got displaced, so I glued it down with a tiny bit over double-sided tape (seen here),. After reassembly, this allowed the disk to depress the volume microswitch again

Can anyone confirm? How did it get loose? What if one of those magnetic disks goes missing? Where to order? the part iFixit is carrying shows no magnetic disks…

Update… Found this repair guide for an iPhone 6. In the comments on Step 34, similar magnets are mentioned. Although the volume buttons, brackets and retaining clips are of different design, they sport the same magnetic disks, acting as a protrusion which actually touches the microswitch on the volume control cable.

Now the question remains. How did the magnet get dislocated in the iPhone 7 Plus I repaired, and if one goes missing entirely, where do I purchase?