What? As a Support, the majority of games I play, the majority of my teammates think I need to be back up heal only when I Champion 
. I am there to support them only to help them stay alive. So when they dive for the kill too close, and I had just healed them to save their life, then the timing is wrong but I am still blamed for their death.
In concern towards your scenario, I too have last striked when maybe they did most the work. There are some whom will tell me I need not to apologize, as we are suppose to kill the enemy anyway. Could be that the specific Teemo 
might have played in some earlier games that day and maybe too many people did the same thing as you did. The concern is if you did that the entire game, then I would be more concerned. Sometimes I will say, Last strike is not usually my game plan when owning the lane with my teammate, I will try to keep last strike to minimal if this is your game style or this games specific practice objective.
I already know I might not top anywhere near the best Team Supports when I prefer to walk with 
when walking/ running as . My reasons is, If I am Team Support, then I am going to make sure to be a First Citizen Responder for my teammates, so in fights I might be able to heal them in their retreats with last health bar frames of life; more than once have performed this gesture. I give them my "W" spell, which is giving them my life for them to live. As far as kills to the enemy, I try, maybe get one, but Assists would be more of my focus, or to make sure they live as is my priority.
As for last strike. Most of the time I am damaging the enemy for my teammates and have no worries at all of winning a game with no kills ever, as more than once I have achieved this reward. This goes to the conditioned of game teammate teamwork support I leaned when there were no thumb controllers for home video game play stations.
As a born leader I am as FuryofThornsRedo, the human being I am, I have been raised in more than one social experience to not build my game focused only on kills. I know there is a strong need to kills enemies in most games to win games, but I take a larger big picture approach. I like tandem throws in trying to defeat the enemy, then the last strike going to the teammate whom has the last strike to throw as in the recharging time for the ability is in the timing as well.
My opinion as a Support, I would state, to focus on Sportsmanlike Conduct as in supporting the definition of sportsmanlike conduct. Play with a positive attitude. Emulate those qualities in which if you had to have some other person support you, treat them with the empathy of placing their needs before yourself. Or, making their needs a priority second to your game objective to be a support inside of you own game plan without being the main reason or cause the positive attitude in the game is less so; which could demean team morale or the environment atmosphere of the game in which your are a teammate: 1 of 5; in other words even when they might say the game loss is the supports fault. There are team wins and team losses. As far as I know there are 5 people to be held accountable for the loss aligned with: timing of maneuvers, strategies, lane fights maybe too soon with too many as distracted from the responsibility of other lanes defense. Walk with dignity and share: Thank you for the game, fun time. No need to share more in a hurtful conversation debate in chat :Champion select, in the game, or at the end. Be patient and calm, then if needs be as in Accordance with the Summoner's Code, report for Negative Attitude, or unsportsmanlike, or the main reason pertaining to your need to report. Remember less negativity, then farther away from Bronze. From: FuryofThornsRedo
<Now the rank is known, and maybe there is much you might already know. This is the thus far from which I have learned as a Team Support along inside of my own learning agilities and abilities.> (Please excuse the length)
and got a double kill mid. My mid says "Why are you KSing as a jungler"? I reply "OK next fight I'll just run around and not Q or autoattack so I won't steal anything". That shut them up real fast.
