What Shari said--it happens to nearly everybody, every time they move up a level.
I'll also add that entries are very, very, very rarely disqualified, and every effort is made to help the writer to make the entry 'legit', if possible. For example, if an entry is over or under the allowed word counts, and if the judges (or word counter) catch it on time, it's pulled, but the writer is notified and allowed to re-enter the piece once they've added or subtracted words.
There have been other, extremely rare, DQs for entries that didn't quite meet the criteria for the contest, but in general, Deb will make every effort to see that entries make it into the contest. And if a person mistakenly enters in the wrong level for several weeks, if Deb eventually becomes aware of it, she'll just send that person a very lovely email saying "time to move up!"
So it's really no big deal at all--and you're very sweet to be worried. That's why I love this website!