I actually read it the first time as Harry goes back, gives Sev the kiss and is attacked at home by a third party a second later before either of them knows what's happening. Perhaps Harry should have been paying more attention to his dueling skills than taunting Severus!
Then, I read it a second time and thought that maybe Severus killed Harry. Would make for a very dark fic!
Interesting drabble. Loved the first kiss! Calling Sev a coward will always get a rise out of him, I suspect. Great way to use that fact, Harry.
The last kiss was important. Always tell someone you love them.