Well, this is definitely a bummer of a situation. In your case, you weren't cheating or trying to get an advantage, but instead you broke a rule. This is one of the most publicised rules, so unfortunately even though a minor offense, you've been convicted of not following directions. I don't believe adcoms would assume you were a liar, cheat, or unethical (unless something else in app points to that??). Here's another thread on this topic: http://gmatclub.com/forum/gmat-misconduct-got-kicked-out-from-test-106642.html
The best you can do is be 100% truthful. Honesty is the best policy. As an unbiased reader, it seems that your explanation of the offense was so minor that no proctor would have even seen or cared about it (or it's extremely harsh). I feel that the phone must make it into your hand and out of the locker before it would be a true violation. So you want to be 100% clear, truthful, and to the point so that no adcom would be questioning your sincerity or dwelling on the topic. Also, don't blame the proctor, rules, harshness of penalty, etc... You should take full responsibility, and show that this out of character for you, and that you've learned a valuable lesson that you'll never forget.
Don't let it get you down too much because what's done is done. Now its time to put together the best application YOU can! This mistake will not keep you from achieving you goals, and hopefully one day you can look back and laugh at this snafu. So few people have the "perfect" application, and wish they could change aspects, this is just something you will have to overcome and address in the optional essay. These types of things are what that essay is for right? Best of luck! PS, come back and follow up with an outcome whenever apps have played out.
To everyone else out there taking the test, LEAVE YOUR PHONE AND NOTES IN THE CAR.
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