It's my own fault, but I set off for work the other night without checking the Pocket (Glove Box?) Lids. Halfway to work I realised that the left hand lid had come off somewhere along a 5-6 mile stretch of road . I did have a somewhat cursory look for it but it was akin to searching for the Holy Grail. Now I'm sure many people have thought about this and attached some sort of retaining wire or similar to the lids - which I shall be doing before I take the bike out again but if this saves anyone else the same problem it'll make me feel better. Replacement lids are available but the cost mounts up when you have to buy the lid, lock, pins etc.

Hand up. Happened to me. Same side.
You never find them no matter how hard you look. The glove box lid fairy makes off with them as soon as it falls off.
Buy another on eBay and don't worry about locking it.
As for losing another, you won't. Your stupidity has now burnt it on to your brain and every time you use one of the pockets in the future, you will remember.
I keep my camera in the right one and leggings in the left. Never had any problems.

I put straps on mine to prevent this. put a snap on each end of them so I can easily remove the lid if needed. Mostly I never need to un-snap them because there is enough play in the straps to allow access to the pocket.

Here's on on UK Ebay, not sure which side. And seems cheap enough to me:

http://cgi.ebay.com/GENUINE-BMW-K100LT-K100-K-100-LT-1987-STORAGE-BOX-LID-/200594637640?pt=UK_Motorcycle_Parts&hash=item2eb45f4348

Two more from USA:

http://cgi.ebay.com/ebaymotors/1985-BMW-k100RT-Right-Glove-Storage-Box-Radio-Cover-_W0QQcmdZViewItemQQhashZitem3367bc7d57QQitemZ220783738199QQptZMotorcyclesQ5fPartsQ5fAccessories

http://cgi.ebay.com/ebaymotors/1985-BMW-k100RT-Left-Glove-Storage-Box-Radio-Cover-_W0QQcmdZViewItemQQhashZitem3367bc7d3aQQitemZ220783738170QQptZMotorcyclesQ5fPartsQ5fAccessories