Measure twice, cut once. Important words, indeed.
As I recall, one of the very first posts I read in Steemit was about someone who had ended up sending a large sum to some account that was "not quite Bittrex" and had lost it all... and I have been utterly paranoid ever since... double and triple checking every wallet address, and when I have larger transfer amounts, chopping them into several smaller bits "just in case."
Sorry this happened to your, my friend... hopefully the universe will reward you back for posting this warning to others.
I was upset for about a day. The actual amount lost was closer to $1000 but it has grown into over $82,000 and could actually end up being much more than that!