I’m just relaying what I read. It could simply be that you had to be on fire from an enemy, not self inflicted. And if self inflicted counted, maybe it had to be by a COV weapon, not a class mod.
The main point I was trying to make: the Lootthemoon web site referenced said it was a random reward, indicating, e.g., that you might have received it simply for being online (even just being idle in sanctuary) at a particular time whereas everyone else on this board did not. I found that to be extremely unlikely and instead think that’s it was tied to doing something, likely with fire–it could be being on fire for a certain amount of time, killing a certain number of enemies with fire from a COV weapon within a certain amount of time, etc. It could be a very narrow thing–kill 10 COV with fire using a COV weapon in 30 seconds while in Ascension Bluff–something very few would do. But that would still mean the reward wasn’t random and instead was tied to doing something.
Having it be tied to some fire based challenge makes more sense than GB randomly sending the grenade to less than 1% of the players in a few week period shortly after launch, never to be explained or mentioned again.
I could be totally wrong, but random mail just seems odd to me (esp. as the site picture shows a level 65 version, which indicates people are currently getting it).