not so as stuff disappears into the void, just changes a sell 100 into a sell 90 for example.
i am not entirely certain things don't go into the void :p but from my eyeballing it's just an entry change rather than a vanishing coins trick.
, go into your trade history and check the numbers in there for differences.
OK again this is normal as far as I can interpret your situation.
You want to sell 100 coins. You put 100 coins up for an X amount.
I want 90 coins for X amount.
The exchange sells 90 of your coins to me. You see a partial sale of 90 coins.
You now have 10 coins for sale at X amount and the money for the 90 coins.