maybe you were drunk and spent them for other ICOs or anything like that :-)

just kidding but I doubt that a hacker gained access to your account because in this case, you would lose all your coins and not only 5.

Even if waves would have a customer care, I doubt that they can offer any help...

I agree that you should take a look yourself to what actually happened.

PS: May I ask when you purchased the coins and to which rate? I am considering buying them as well...

Take care and all the best