WhatsApp can be hacked or not ?

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My android phone is damaged before 2 months and from that time I dont have a smart phone so I started using WhatsApp via bluestacks which I have installed in my laptop.Few days ago when I started my bluestacks WhatsApp stoped working and I have to reinstall it again but I found that it didn't backed up all the messages till the date I used my WhatsApp account some of my very important messages are lost..so I thought it had been hacked by someone else..Is it possible?