I am a Nigerian and I know how Nigerians behave. And as at 2011, the value of N100k was very high that it could buy you a plot of land in some mini cities. There is no how you will invest N100k by then as a Nigerian and became carefree about it.
By that time you mentioned, it is only a few people that could invest more than N10k in an online business they consider a ponzi scheme. I am sorry, I do not believe your story.
I was about to mention that also because the story looks like a made-up story because I also from the same region know the extent to which bitcoin adoption and awareness have gone in Nigeria for ops to have invested 100k into bitcoin as far back as 2011 when bitcoin was still trying to gain users attention and at a low price, there is no possibility that the ops would invest such amount in bitcoin and entirely forget to preserve the private keys to that wallet.
Ops need to come up with a more clear statement unless he is just dealing with and living in an imaginary world, and even at that, the reality is that he will have to know that only the private keys to the wallet prove ownership of the funds in it.