If you want to be refunded a skin, you would have to be able to prove that you did actually lose it for no reason and that you didn't trade it away, sell it, etc.
If you have a recording or something of the like of the time that you lost it then we would be able to do something about this.

In regards to the reports about items disappearing, I am looking into it, however it should not be physically possible for items to randomly "disappear" at all.