300 BTC is a huge amount today, but when I lost it, it's only worth about US$4000 and I determined it's not the end of the world even if I lose it, so I took the risk.
Fortunately, I still have some BTC left

Lost 300 BTC by "investing" in BTCST .......

300 Bitcoins?

Who told you to put all your eggs in one basket? This mostly happens when people don't think before investing somewhere or when they get greedy to earn a lot of money at once and in that hurry they just do it without any research or something about that source they are investing with.
I am sorry to say and I really feel bad if you lost this much amount, but this sounded like a fake post to me. I mean come on a member who has lost will take a minute to tell us what exactly happened and how he lost such huge amount.
That looked like he just wanted to make a post, that's it.