I'm beginning to think Sir Isaac Newton drew the wrong conclusions when the apple fell on his head: what goes up does not necessarily come down.

The reason for my growing doubts about gravity is not an apple but a rather large suitcase weighing 20kg. As far as I can ascertain, it left Heathrow airport on a plane last Thursday but never returned to earth. Presumably it is still floating above the clouds, somewhere between London and Damascus.

Judging by reports on the internet this is by no means an uncommon occurrence. If you fly fairly regulary it's almost a statistical certainty that your bags will vanish into thin air at least once during your lifetime - and it happened to me last week.

To be stranded in foreign parts with only the clothes you are wearing is a disconcerting experience and it's not something that airlines or airports are particularly adept at dealing with, as I have been finding out over the last few days.

The problem has also been made worse by the recent security alert in Britain, with airlines now urging passengers to keep hand baggage to a minimum. Flying for the first time since the alert, I followed their advice and took only a small carry-on bag containing my laptop and just a few bare essentials such as money and travel documents, plus a book and iPod for the journey. Everything else went in my now-vanished suitcase.

Arriving at Damascus airport I stood by the conveyor belt, becoming increasingly impatient as other passengers collected up their bags and left. Finally, the conveyor stopped - with me still waiting. In the "Lost and Found" office a man entered details in a computer as I pointed to a chart on the wall showing various shapes, colours, handles and wheels. "Call us at this time tomorrow," he said hopefully.

I left the airport in a strange sort of limbo. Possibly my bag would arrive on the next flight, possibly it had had been sent somewhere else by mistake, and possibly someone had stolen it. I had no idea which, and nobody seemed able to tell me. If it didn't turn up soon I would have to replace some of my missing belongings, and what had started off as a working visit to Syria and Lebanon could easily turn into a shopping expedition.

Checking the hotel bathroom I was grateful to find a plastic razor already provided, along with a makeshift toothbrush and a micro-sized tube of toothpaste. At least that was something I needn't bother about but, with a busy morning of meetings ahead (including a government minister) I had no choice but to attend them in jeans and a sports shirt.

A series of phone calls to the airport and the airline over the next few days failed to elicit any information as to the whereabouts of my bag, or possible compensation procedures. The travel agent in London had nothing much to suggest beyond saying "It's always a palaver when bags go missing". Indeed it is.

Trying to recall what was in the bag, I made a list of more than 30 items and the shock came when I started adding up what they had cost. Including the suitcase itself, it was somewhere in the region of £500-£600.

For the moment, though, my bag is officially classified as missing. Since 98% of missing bags turn up eventually, I may have to wait three weeks before it can be regarded as permanently lost.

Browsing through several websites that give advice about missing or lost baggage (here and here), it appears that airlines usually wriggle out of paying the full replacement cost and often try to exclude certain items if they think you shouldn't have been carrying them in as checked-in baggage.

"The sad reality is that you'll probably end up quite severely out of pocket," one of them warns.