It auto sold on coinbase when it was rec'd and I did not know of the mistake of him sending double for 2 weeks.
If this is the case, can you provide documentation that your coinbase account was setup to automatically sell any bitcoin it received (or that the sale in question was an "auto sell") and that you were in fact hospitalized for two weeks? I am not familiar with casinobitco.in so I cannot speak with them withdrawing the entire balance, and I have never used coinbase to automatically sell like that (nor did I know this was an option unless you were setup to be a merchant). This is obviously sensitive information, so if you were to share it, I would suggest that you only share it with BigBiz with his promise to keep it private.
If you can document the above then you do have somewhat of a case. I would suggest seeing what BigBiz is willing to accept, as I assume that he will not accept $275. I have seen this case a few times, however the above facts are new to me, so maybe BigBiz does not know this (?). I would say that regardless you do owe him the 2 BTC but he should be willing to work with you somewhat if you can prove that circumstances outside of your control caused part of this situation.