I have had this type of trade placed several times in the past and you will see it regularly take place if you have stops placed that are visible. Stops are quite often targeted as this is easy money for brokers and market makers.
There several ways around this, the most obvious is trade longer term with trends and have enough capital to cover swings. The other which actually goes with long term trading is manually place stops by placing a close trade, not a stop loss visible order.
What I suspect has happened in your case is your chart is only showing median, open, closed or low prices and not 'high' which is maybe where your order was taken.
FX can be quite ruthless to say the least, it is all run by professional market makers with one aim in mind, Get Your Money! They do not know you and don't care who you are. It is a fact that just over 90% of FX traders lose money trading FX. If you don't believe what I have said here just try placing a trade during a quiet period of trading where there is low volume and you will see the price take opposing directing to your trade every time, albeit it may only last for 20-30mins or so.
Thos who object to the above statement will be working for or are brokers and will defend such comments to keep as many people trading FX as possible.
Just my experience after 13 years trading.