I then logout and login again but all my bitcoins had gone.
Something like this happened to me. There is no e-mail verification and what I learned is I had signed up initially where I had typo'd on my e-mail address. Then when I went to log in the second time, it was a completely different account, with zero balance.
Fortunately I was able to figure out my typo by trying common mistakes I've made before and sure enough one had my funds.
One way you are able to tell if this is what happened is to look at the history.
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http://kingco.in/history.php <-- Click on My Games.
If you played previously and nothing shows now, then you are on a different account. If that is what happened, maybe coolidgecoin can help clue you in as to which e-mail address you might have used.