TTN, My grandfather left me his brother's medal set Pip, Sqeak and Wilfred plus the DCM - unfortunately they went missing while on loan to family member who died suddenly.
SLXOwft sorry to hear that but unfortunately it is a common tale. You might try contacting Medal News, which is produced by Token Publishing (Google them for contact details). I understand that they have a section where you can post details of lost or stolen medals. You will need as much information as possible as regards the naming on the medals (number, rank name and unit). Also if you want to let me know this info by private message I can post it on a couple of Facebook groups connected with medal collecting I am a member of. These may be long shots, but worth a try.
A few months ago I went in for surgery. The anaesthetist knew I was ex-service, and as I was going asked "last three". A bit of a surprise, but I told him, just before I went out. Not been asked that for well over thirty years
As regards everyone remembering their own number till they shuffle off, I once had medals and a lot of paperwork which had belonged to a Grenadier Guards officer back in the 1930s/40s. Among the papers was a letter he had written, post retirement, to his regimental HQ asking them if he could be reminded of his service number. Obviously guards officers rarely had to quote their "last three"!