We use Facebook daily to do conversation with our friends, relatives and sometimes with our profession clients too.
It's very important for us to get those conversations back if mistakenly they can deleted.
Some common situations that lost Facebook private messages you can recover from:
1. accidentally deleted it on your android phone
2. lost messages after Android 5.0 updated or other Android upgrade.
3. save messages from water damaged, crashed, broken or smashed Android phone
4. Android delete facebook messages randomly by itself
5. Factory restore Android phone.
And more...
With this way you can recover deleted messages on any brands of Android device such as Samsung, HTC, Huawei, Sony, Motorola, Lenovo, LG, Sharp, etc.