If you ask the suppliers the may have tracking numbers for the packets, then you can look the up here click here if they were sent by Royal Mail or here if Parcelforce click here;jsessionid=2ZMPC15GXAQNKFB2IGEENZQUHRAYUQ2K?catId=7500082&pageId=trt_resultspage&keyname=track_blank&pfHomeTrack=true&_requestid=7078
I sold 13 new boxed unused mobile phones that were surplus to requirements (the company updated its car kits and the older handsets no longer fitted). I packaged them all up the same, bubble wrap, brown paper and parcel tape and sold them on e-bay over about five days for around about £15 ish each. All posted at the same post office and I got receipts. Two didn't make it and although I put a claim in and the Post Office gave me the money back, it didn't do much for my e-bay standing (fortunately the buyers were good about it). The money was donated to charity so they didn't lose out but the Post Office did, which means we did in a round about way. It's not a terriby good success rate and as you suggest,it means either incompetence or thieving.