Completely Ran-dumb!

About a week ago, I had a somewhat strange encounter that I thought was slightly awkward.  When I arrived to work, I was greeted by a man in the parking lot.  As we were walking in the opposite directions, I initially thought his acknowledgement was just a friendly gesture.  He even complimented the necklace I had on, and asked if he could take a picture of it.  As he was talking about how the necklace was, somewhere along the lines of, "cool and artsy," he suddenly sees my sketchbook and asks if he could "check it out."

the 'artsy' necklace I was wearing at the time

Just as I hand him my sketchbook, he all-of-a-sudden has to leave because the people he was with (family perhaps?) were waiting for him.  As he is anxious to get on his way, he asked, "Do you trust me?!"   He then asked where I was going, as his implication was to take MY sketchbook along with him, then eventually meet with me later to return it.  He noticed my hesitation and later identifies himself as a military sergeant and flashes his driver's license and military ID.  Then as a trade-off, he hands me his digital camera for security purposes.  Basically, since he had my sketchbook, he gave me his camera as sort-of a collateral for when he eventually returns........weird.  Fast forward to later.....

The guy eventually shows up at my work, with my sketchbook.  I saw him from afar and came over to greet him.  As I extend my hand, expecting to shake his, he ends up simply slapping the book into my hand and says, "What did you expect?!"  Then just walks off.  Wtf?!  On top of that, I also notice something added to my sketchbook. Not only on the inside, but also on both the front and back covers!

The cover of my sketchbook is covered with stickers/decals that I've collected and attached myself.  One of which, is a mustache sticker on the front cover.  So when the book was returned to me, I noticed that there was a face drawn on the cover, as part of the mustache!!  Then, I found out that there's also a drawing on the back cover as well.  Later, I discover a page that has been completely covered in.....nonsense/chicken scratch/creative expression/I don't even know what.

Front cover: my mustache sticker with his added face

"Bye-Bye," on the back cover

The hard-to-read page in the middle of my new sketchbook

At this point, I'm totally confused.  Who does something like that?!  I was a little taken back by the whole thing.  I wasn't sure how I should be feeling.  Part of me was thankful for his "artistic" contribution, but another part of me was a bit upset at the disrespect for another person's personal belongings.  It's one thing to borrow a sketchbook just to look at, or gain some insight, or get inspiration...but I felt that it kinda crossed the line when I didn't get it back in its original condition, only to be surprised at what was found.

Before, I was debating whether or not I should remove the page from my sketchbook.  Had I known he would be adding a page to my sketchbook, I would have added more photos to his digital camera.  But  now, although I'm not really fond of looking at it, it merely serves as an interesting conversation starter.