And what happens to the virtual memory in the RAM stick? nothing seems to happen on the computer
ReadyBoost is not virtual memory, it is a harddisk drive cache. Windows would rather use your RAM as a cache, but if that's low, solid-state memory is a decent second option.
Reading and writing small files in solid-state memory is faster than on a harddisk drive. Windows copies regularly used files to the ReadyBoost drive so it can load them faster in future. If Windows can't find what it wants on the ReadyBoost drive, it goes back to the harddisk drive.
Everything is always saved on the harddisk drive, so removing the ReadBoost drive does not cause any problems. Removing the ReadyBoost drive only increases the time taken to access cached files in future.