Guardian Angel doesn't reset once it goes off cooldown.

So during my last match I bought a Guardian Angel. At one point I died, and shortly before a teamfight I watched the last few seconds tick down to 0. Now during that teamfight, as I was being jumped by a J4 I noticed the GA particle was missing even though the timer had ticked down to 0, so I died. Here's the Link to the specific Match, if it helps. I can't really make a video on it because I don't think the replay system shows item cooldowns, does it?