Difficult one Debbie. The security implications of your enquiry might be the main hurdle. You could try their respective MCM Div at the Army Personnel Centre, 65 Brown Street, Glasgow if you know their capbadge, alternatively try their Regimental Association or take out a small ad in Soldier magazine. If you know where and with whom they were alst serving, you could try the unit, although with the exception of the Soldier ad, you will have to explain why you are trying to contact them and who you are.
As we are caring and sharing here at ARRSE, in addition to the above searchers scouring every last nook, cranny and Revel packet in the UK, I have telephoned every Regiment and unit in the British Army and (alas and alack ) all say they have no one matching the description you have given. This is some what strange as it was such a good lead.
Knowing how you feel about losing things (see post above regarding TV remote) I feel I should help you.
So what you need to do is sit down in a quiet place and think. Go over in your mind when you last saw him, where were you?, what were you wearing (have you checked your pockets?) did you go any where? perhaps you left him at Tescos! or round at your aunties house when you went for tea last Sunday week.
Have you telephoned the Police to see if he has been handed in? Or if you are a regular user of Public Transport try the local bus company lost property office.
If all else fails go out and get a new one and as soon as you do he will turn up