Oh man, it sucks! I would like to tell something good to you, but I'm afraid it's not very likely that you will be able to return your BTC. I only can wish you to get well soon!
If you're going to leave coins on an exchange at least choose one of the larger ones which have been around for some years - but even then there are no guarantees.
It's never a good idea to leave coins on exchange for a long time, no matter reputable this exchange is. Cryptopia was pretty big exchange and they've been in markets for long time already, there was no red flags about this exchange as I remember and you see what happened.
The best solution is to buy hardware wallet to store your btc thete rather than storing it on an exchange to avoid losing your btc.
I'm afraid it's too late to suggest it. And people who aren't looking into crypto very seriously aren't likely to consider to spend ~$100 to buy hardware wallet. Sometimes like in OP story, people sometimes don't even bother to setup proper desktop or even web wallet. They rather leave coins on exchange.