Surveyor Rant lol

I just hunted a surveyor south of the southern station on buried. I threw a total of three showstoppers, three seeker nades, and a impact grenade, along with ~7 shots from the renegade, which did kill it, exhaustingly enough. My problem isn't even it's defense, but I see videos that say and show them getting at least a couple surveyor vaults, why am I getting none? Two dead surveyors on my codex, 0 surveyor vaults collected, what's the deal? Is this common or am I unlucky?