I have killed 3 tormented bosses (first time on my account) and received 3 sparks (1 from each) which is fine. Now I completed lvl 18 at Iron Wolves to collect the 4th and it was in the bag which is fine too. After I looted the 4th now in my inventory it shows that I only have 2… So 2 of them gone missing. I collected all the sparks with one seasonal character, very first time killing tormented bosses on my account (at all, not just this season) and very first time completing the iron wolves lvl 18. Never ever used any of those sparks, so it is definitely a bug. GMs confirmed that it is a bug and asked to be patient till devs fix it…
edited after 24 hours: it is a bad joke, that after 24 hours and 4 GM replies they confirmed several times that it is a bug, but they haven’t refunded the sparks even if they know that it is a bug. GMs keep writing useless messages instead of fixing the issue… Anyone understands what are these guys doing at Blizzard?