Based on the past event I think that 999dice.com is really a scam site.
https://bitcointalk.org/index.php?topic=386238.msg4159346#msg4159346https://bitcointalk.org/index.php?topic=376783.0
I think that before you play at any site that you find on the internet I think you should probably use these keywords over a google search engine or any similar search engine "(name of the site with .com) trusted".
If you are playing with bitcoin then most probably that the site has a past thread here in this forum and most likely that you will know its history whether the site is good to play or a scam one.
Before you play again on any other site please do a background check first to prevent any scam issue that you might face when playing in an unverified gambling site.