That's just part of bowhunting. Sometimes they sneak-up on you. I didn't see the buck I ended up killing until he was literally 5 yards from me. Same situation, except I ended up getting an arrow in him.

Hang in there, and in the future be patient, and move when you can! Don't loose too much sleep over it. Just another classic example of learning from a mistake. That's the best way to learn my brother!