UPDATE - I (20F) Found a photo of a woman in my dad's (52M) wallet

Original post
I am really grateful for the advice I received. I decided to ask him about it last week when I was over there house.
It turned out it was a picture of his Fianc?e who had passed away after an accident. He had completed his undergrad and masters in another country, They had met in the first month of college and instantly fallen in love. They stayed together while they completed their education and He had proposed after he got a good job. She passed away just three weeks after they had gotten engaged. He decided to move back as he wanted to spend time with family,
I would have never guessed this, He has always been a chilled out person, always happy and calm and I can't imagine how he could over come losing someone he planned to build his life with at such a young age. I teared up a little when he was talking about it. which is a bit silly, while he was very calm and collected.
I am a bit guilty for jumping to the worst conclusion quickly and without Dating.mobi's advice I would not have had the courage to ask him about it.
TL;DR - It was the pic of my dad's Fianc?e who had passed away after an accident.


Source.