It may happen not only in Bitvest, it may even happen to casino with an active representative in this forum and the worst case (site turn to a scam) is that you may not even able to reach the representative although they are still active in this forum.
This is why it is always recommended to players to not hold money in a casino's account for long time.
Once we done with our gambling session, better to withdraw it but if anyone want to hold some, it is better to hold not big amount of money.
The most important thing for us as gambler is that we should have a mindset that we are the first one who responsible to what we do.