It depends on what your location is.. Is any of the product missing? maybe a crooked postal employee or customs agent saw a package from Amsterdam and needed some free mda (or what he thought was MDma)
I'm in Ireland and as a matter of fact there was some missing about half a gram.
It's self explained, then.
Somebody on the mail chain helped himself and tried to cover the theft. I would stop worrying if I were you.
This thread is deteriorating into a farce, are you seriously suggesting a customs inspector would go to the trouble of opening and removing .5g of mdma for themselves then tape it all up again??
Get a grip, if customs found it they would seize it, all of it. If the customs inspector was a did dodgy and had a mind to 'steal' it they would have just stolen the whole thing, again VERY VERY unlikely.
If they let it through to track it you would not have a clue it had even been opened, they are very good at opening and resealing things for investigation purposes and Ireland's customs are pretty tight from what I read on here.
Who the fuck knows what happened to it, maybe the vendors runner fucked with it before posting it, maybe your postman likes to go raving, maybe this is all a load of bollocks.
Bottom line is you got your drugs, well most of them, stop ordering to your home address.