All gone, Files disappeared from Document folder

[Favtech]

My contacts has gradually be disappearing from my phone, today I discovered that all my PDF files under document fold is gone, completely gone without explanation or reasons. My phone is kindof now empty except for pictures and few files from whatsapp and telegram, Please help

[BandOfBrothers]

If this was my situation the first avenues I'd be looking at is what my phone is set up to sync with @Favtech