This is an oversight on the part of FortuneJack and you do not want to take any responsibility. According to your TOS you will do reasonable effort to try and contact the user. I have no doubt that you take the time to contact your users to avoid this situation, but in 2016-2017 this was clearly not the case. The fact that you did not try to rectify the situation clearly demonstrates a lack of professionalism.
Very disappointing,
You might be disappointed and I'm sure most people will feel the same as you including me but we should also realize that it is also part of our own fault where we forgot about our money in online services. It is true that any online services should remind their players once the accounts are going to be closed, in this case FJ claims that they have informed you but you claim that you have never received any email from them. All in all, there is no way for others to prove which claim is true.
I was fairly new to crypto, and thought I lost it all. This happened with one other casino and this was there reply:
Hello, your archived account balance on Betcoin.ag is 0.044703 BTC. If you are located within a permitted region, please
create a new account and we can offer you a bonus to welcome you back.
Thanks,
Betcoin Support
And they gave me back my balance. Not saying what Fortune Jack has done is illegal. Simply saying that they don't care of their customers and you should maybe play elsewhere if you think they care. They have never reached me or try, they will for sure never handle this with some compassion or try to help even with a small bonus. Just sharing my story