That is almost certainly why, next time if you look by the system tray (Where the clock is bottom right of screen) you will see an icon appear when a mass storage device is connected such as the USB stick. If you click on this a sub menu appears with the device(s) connected, if you click this then select your stick then say ok a baloon will appear saying it is now safe to "Disconnect the device".

As to the PC shop I am doubtful to be honest but worth a shot, I am in this line of work myself not a PC shop that is. (I would have a look for you but your no where near me unfortunatly) generally most PC shop's will only deal with PC'S, certainly do not go to the likes of 'Tech Guys' if A) You value your data B) You don't want a wasted journey.

A "Check disk" may well help you and is something you can do yourself?

Martin