0.4 is not a small amount to take it for granted and not to use your own wallet to keep it, I think you are investing without educating yourself on how to keep your investment in a correct manner, honestly there is no such thing as stable exchange, there's always a possibility of hack, in your case the exchange is already gone, and it will take a lot to get those Bitcoin back, I'm pretty sure you know what you are going to do, it's a lesson learned.
Small amount? the OP says he invested in jan if it was jan 2018 then the fiat value equivalent to 0.4 BTC is not small. Learning which costs 0.4 is actually huge cost for this learning.
I'm pretty sure he's not saying it's small but rather saying that 0.4 is not a small amount. Heck compared to the first few years of bitcoin, any price of the current BTC is enough to say as not a "small amount". Well, I'd agree with others that OP already lost those 0.4 BTC he/she had back then. It's his/her fault for not managing it well enough. We all know that investments are supposed to be managed even if not 24/7, at the very least, spend some time to check it out at least once a day.