Got an email from mgtox asking for the reference number and stating they would look into this.
I sent them the reference number from my account history.
I am at the same point currently. I received a similar email on the same day as your post.
I also am at this point, but no email responses from them what-so-ever. I did send all the vital information they need to track the issue. My missing funds are from a transaction this last Sunday (server time ... UTC?).
06/05/11 16:07
Transactions before and since have processed properly and landed in the same account, so I am frustrated that the middle one would disappear [also my largest transaction with them].