I've finished all ten missions. Where's Vettenmyer?

Hint 1 of 12:

Have you been keeping track of all those notes he's left you?

Hint 2 of 12:

Do you notice anything in common between them?

Hint 3 of 12:

No, it has nothing to do with his insults.

Hint 4 of 12:

There are numbers in each message.

Hint 5 of 12:

Have you noticed that each number is only used in one message?

Hint 6 of 12:

Putting the messages together by number will help.

Hint 7 of 12:

Of course, all those sentences make for a very long message.

Hint 8 of 12:

Put together the first letter of each message.