I haven't used slush's pool in quite some time, so I don't know if anything changed or not.
In short rounds, not everyone has a chance to submit shares. The higher your hash rate, the better chance you have of getting a few shares in a short round. If you do submit a decent amount of shares, you will get a decent pay out.
OP, I would assume that you submitted 0 shares for that 35 second round. Are you 100% certain you submitted shares for that round? From your very small payouts on the other rounds, I have to assume you hash rate is quite small and that you simply did not submit any shares for the short round, and therefor received no payout.
As the previous poster mentioned, perhaps any shares you did submit were stale.
Simple answer: You must submit shares to receive a reward.
I remember the 3 second round on slush's pool that has 8 shares submitted. Lucky I managed to submit one of those 8 shares. That was a 6 coin payout per share!