I clicked to queue for a match, then realized I didn't have time to play in a game and canceled after 3 seconds. I was reading the comments posted in the Lobby for about 15 seconds and everything was fine. I then went to check Facebook and watched a YouTube video. When I came back to Card Hunter apparently I had been placed into a match and had timed out. It wouldn't normally be a huge deal, but losing 20 to 30 Elo due to not even knowing I was in a game is kind of weird... especially when I waited a good 15 seconds after I had canceled the queue. I know sometimes it makes a match and will assign you an opponent even if you've quickly canceled, but that happens within a second or two afterwards -- not 15+ seconds later... Just a bit annoyed that it happened, but figured I'd report it so someone can look into it so it doesn't happen in the future.
It sounds like your cancel request came in too late for you to be taken out of the queue. I would have thought you'd seen the response within 15 seconds though unless the server was under very heavy load (unlikely).
Yeah, I've seen it do 5 to 10 seconds before, which is why I always wait a good 15 seconds. This was definitely over 15 seconds though.