No sadly ne never talked about it or mentioned anything in regard to crypto. That is what it makes it strange.
~snip~
This is nothing strange, considering that the wallet is from 2013, it is possible that your friend invested some money in BTC then and completely forgot about it. Besides, it is not advisable to talk about such things, and maybe he was aware of that.
this is also the first thing that came to my mind, keeping the old wallet in his desktop, it means OP's friend is holding something, it's possible that he has an investment held there. When it comes to our investments, we usually don't even inform family members because they are considered as confidential things for me. The situation is difficult if the sudden disappearance of a person and then the investments or properties are not left to the families, it is quite difficult to recover especially since there is no other lead and there is no consent from the owner.