Unknown WeaponID

I’ve just had a go at collecting weapon stats from games and have found a WeaponId that is not in the Metadata.

It’s the first game I’ve tried to collect so it’s possible I’ve done something wrong but.

MatchId: 740b859c-16ba-4cf0-98de-92c73a7f35b2

StockId: 2457457776
Attachments: none
TotalShotsFired: 0
TotalShotsLanded: 0
TotalHeadshots: 0
TotalKills: 0
TotalDamageDealt: 0
TotalPossessionTime: 00:00:00.8500000

The player is “Colossal xo”

Any ideas? Is this a bug? Do you just ignore this WeaponId?