Guardian Angel failing to proc?

I've only seen or experienced this bug once, and haven't had anyone to attempt to replicate it with. I was playing a 5v5 on Caitlyn the other day, and I bought a Guardian Angel. When I encountered and fought the enemy teams Warwick at dragon, my Guardian Angel (that was freshly purchased, not on cooldown, I hadn't died or anything silly like that) failed to activate when he killed me. They received the gold immediately and my death timer started, screen greyed out, and my death was announced, as normal. My GA went on cooldown immediately, and went through the animation; my corpse fell over, the noise and visuals played, and then my corpse stood back up again. While I was dead.

Both teams saw and acknowledged this, and my corpse possessed sight of the area around it, though being untargetable and completely inanimate. When I respawned it vanished. This is a pretty specific but significant bug, because whilst the situation seems to be very unlikely (I haven't heard of anyone having this issue) it could lose an entire game by happening at the wrong time.

I cast my E into Warwicks face as I died, he was doing heavy on-hit magic damage due to devourers, and he may have smited me with Skirmishing Saber. I don't know if he q'd me or not as I died.

I'd check the death recap, but the Match History function on the website keeps loading my last few games, then saying "Error 404: summoner not found" the moment I try load any further back games. Sorry for being so unhelpful, but I'll post the stats and try replicate it when I can. If anyone else has been in a game where this is happened, please share. I'd love to know what actually -causes- this, or at least have a vaguely better idea of the circumstances required.